2026-11-12 03:06:12 +00:00
28 changed files with 1045 additions and 117 deletions
@@ -2,6 +2,12 @@
 # It is not intended for manual editing.
 version = 4

+[[package]]
+name = "autocfg"
+version = "1.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f2032f911046de80f0a198e0901378627c33f59ea0ac00e363d481118bd70a53"
+
 [[package]]
 name = "compiler"
 version = "0.1.0"
@@ -38,9 +44,53 @@ version = "2.8.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf8baf1c55e62ffcace7a9f06f4bd9cd3f0c4beb022d3b367256b91b87513d98"

+[[package]]
+name = "num-bigint"
+version = "0.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c89e69e7e0f03bea5ef08013795c25018e101932225a656383bd384495ecc367"
+dependencies = [
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-integer"
+version = "0.1.47"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7ce2d95d4b3734dc35aa2f45e1aa22cd416814592a4f9d9205e11affd5b8e10b"
+dependencies = [
+ "num-traits",
+]
+
+[[package]]
+name = "num-rational"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f83d14da390562dca69fc84082e73e548e1ad308d24accdedd2720017cb37824"
+dependencies = [
+ "num-bigint",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-traits"
+version = "0.2.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "071dfc062690e90b734c0b2273ce72ad0ffa95f0c74596bc250dcfd960262841"
+dependencies = [
+ "autocfg",
+]
+
 [[package]]
 name = "objects"
 version = "0.1.0"
+dependencies = [
+ "num-bigint",
+ "num-rational",
+ "num-traits",
+]

 [[package]]
 name = "peg"
@@ -114,7 +164,7 @@ checksum = "e7a5d71263a5a7d47b41f6b3f06ba276f10cc18b0931f1799f710578e2309348"
 dependencies = [
 "proc-macro2",
 "quote",
- "syn 3.0.9",
+ "syn",
 ]

 [[package]]
@@ -167,6 +167,16 @@ pub fn analyze(root: &AstRoot, options: &CompileOptions) -> Result<SymbolTable,
                    StmtKind::Expression(expression) => {
                        root_scope.expression(expression, &globals)?
                    }
+                    StmtKind::If(_) | StmtKind::While(_) => {
+                        let statements = std::slice::from_ref(statement);
+                        collect_locals(
+                            statements,
+                            &mut declared,
+                            &mut root_scope.scope.layout.names,
+                        )?;
+                        globals.extend(root_scope.scope.layout.names.iter().cloned());
+                        root_scope.statements(statements, &globals)?;
+                    }
                    StmtKind::Return(_) => {
                        return Err(error(statement.span, "return outside a function"));
                    }
@@ -207,21 +217,38 @@ fn function_scope(function: &Function, globals: &BTreeSet<String>) -> Result<Sco
            .push(parameter.name.text.clone());
        builder.initialized.insert(parameter.name.text.clone());
    }
-    for statement in &function.body.statements {
+    collect_locals(
+        &function.body.statements,
+        &mut locals,
+        &mut builder.scope.layout.locals,
+    )?;
+    builder.statements(&function.body.statements, globals)?;
+    Ok(builder.scope)
+}
+
+fn collect_locals(
+    statements: &[frontend::ast::Stmt],
+    locals: &mut BTreeSet<String>,
+    layout: &mut Vec<String>,
+) -> Result<(), Diagnostic> {
+    for statement in statements {
        match &statement.kind {
-            StmtKind::Binding(binding) => {
-                declare(&mut locals, &binding.name.text, binding.name.span)?;
-                builder.scope.layout.locals.push(binding.name.text.clone());
+            StmtKind::Binding(b) => {
+                declare(locals, &b.name.text, b.name.span)?;
+                layout.push(b.name.text.clone());
            }
-            StmtKind::Assignment(assignment) => {
-                if locals.insert(assignment.name.text.clone()) {
-                    builder
-                        .scope
-                        .layout
-                        .locals
-                        .push(assignment.name.text.clone());
+            StmtKind::Assignment(a) => {
+                if locals.insert(a.name.text.clone()) {
+                    layout.push(a.name.text.clone());
                }
            }
+            StmtKind::If(b) => {
+                collect_locals(&b.body.statements, locals, layout)?;
+                if let Some(other) = &b.otherwise {
+                    collect_locals(&other.statements, locals, layout)?;
+                }
+            }
+            StmtKind::While(b) => collect_locals(&b.body.statements, locals, layout)?,
            StmtKind::Declaration(_) => {
                return Err(error(
                    statement.span,
@@ -231,39 +258,7 @@ fn function_scope(function: &Function, globals: &BTreeSet<String>) -> Result<Sco
            _ => {}
        }
    }
-    let mut returned = false;
-    for statement in &function.body.statements {
-        if returned {
-            return Err(error(
-                statement.span,
-                "statement after return is unreachable",
-            ));
-        }
-        match &statement.kind {
-            StmtKind::Binding(binding) => {
-                builder.expression(&binding.value, globals)?;
-                builder.initialized.insert(binding.name.text.clone());
-            }
-            StmtKind::Assignment(assignment) => {
-                builder.expression(&assignment.value, globals)?;
-                builder.initialized.insert(assignment.name.text.clone());
-            }
-            StmtKind::Return(statement) => {
-                if let Some(value) = &statement.value {
-                    builder.expression(value, globals)?;
-                }
-                returned = true;
-            }
-            StmtKind::MemberAssignment(assignment) => {
-                builder.expression(&assignment.object, globals)?;
-                builder.expression(&assignment.value, globals)?;
-                builder.intern(&assignment.name.text);
-            }
-            StmtKind::Expression(expression) => builder.expression(expression, globals)?,
-            StmtKind::Declaration(_) => unreachable!("nested declaration rejected above"),
-        }
-    }
-    Ok(builder.scope)
+    Ok(())
 }

 struct Builder {
@@ -300,6 +295,88 @@ impl Builder {
        }
    }

+    /// Function-scoped locals; branches merge definite initialization. A loop
+    /// may execute zero times, so its writes do not initialize later reads.
+    fn statements(
+        &mut self,
+        statements: &[frontend::ast::Stmt],
+        globals: &BTreeSet<String>,
+    ) -> Result<bool, Diagnostic> {
+        let mut returned = false;
+        for statement in statements {
+            if returned {
+                return Err(error(
+                    statement.span,
+                    "statement after return is unreachable",
+                ));
+            }
+            match &statement.kind {
+                StmtKind::Binding(b) => {
+                    self.expression(&b.value, globals)?;
+                    self.initialized.insert(b.name.text.clone());
+                    if self.scope.kind != ScopeKind::Function {
+                        self.intern(&b.name.text);
+                    }
+                }
+                StmtKind::Assignment(a) => {
+                    self.expression(&a.value, globals)?;
+                    self.initialized.insert(a.name.text.clone());
+                    if self.scope.kind != ScopeKind::Function {
+                        self.intern(&a.name.text);
+                    }
+                }
+                StmtKind::MemberAssignment(a) => {
+                    self.expression(&a.object, globals)?;
+                    self.expression(&a.value, globals)?;
+                    self.intern(&a.name.text);
+                }
+                StmtKind::Expression(e) => self.expression(e, globals)?,
+                StmtKind::Return(r) => {
+                    if self.scope.kind != ScopeKind::Function {
+                        return Err(error(statement.span, "return outside a function"));
+                    }
+                    if let Some(e) = &r.value {
+                        self.expression(e, globals)?;
+                    }
+                    returned = true;
+                }
+                StmtKind::If(b) => {
+                    self.expression(&b.condition, globals)?;
+                    let before = self.initialized.clone();
+                    let yes_return = self.statements(&b.body.statements, globals)?;
+                    let yes = self.initialized.clone();
+                    self.initialized = before;
+                    let no_return = if let Some(other) = &b.otherwise {
+                        self.statements(&other.statements, globals)?
+                    } else {
+                        false
+                    };
+                    self.initialized = if yes_return {
+                        self.initialized.clone()
+                    } else if no_return {
+                        yes
+                    } else {
+                        yes.intersection(&self.initialized).cloned().collect()
+                    };
+                    returned = yes_return && no_return;
+                }
+                StmtKind::While(b) => {
+                    self.expression(&b.condition, globals)?;
+                    let before = self.initialized.clone();
+                    self.statements(&b.body.statements, globals)?;
+                    self.initialized = before;
+                }
+                StmtKind::Declaration(_) => {
+                    return Err(error(
+                        statement.span,
+                        "nested declarations are not compiled yet",
+                    ));
+                }
+            }
+        }
+        Ok(returned)
+    }
+
    fn expression(
        &mut self,
        expression: &Expr,
@@ -2,7 +2,7 @@ use endor_core::{
    CodeLayout, DecodedInstruction, EndorCode, EndorNumber, Instruction, ObjectRef, Opcode, Value,
    Vm, VmError,
 };
-use frontend::ast::{AstRoot, Decl, DeclKind, Expr, ExprKind, Stmt, StmtKind, UnaryOp};
+use frontend::ast::{AstRoot, BinaryOp, Decl, DeclKind, Expr, ExprKind, Stmt, StmtKind, UnaryOp};
 use frontend::{Diagnostic, DiagnosticKind, SourceUnit, Span};

 use crate::{NameBinding, Scope, ScopeKind, SymbolTable, diagnostic};
@@ -115,6 +115,7 @@ struct Emitter<'a> {
    source: &'a SourceUnit,
    instructions: Vec<Instruction>,
    constants: Vec<Value>,
+    jumps: Vec<(usize, usize)>,
    children: Vec<(usize, CompiledCode)>,
 }

@@ -125,6 +126,7 @@ impl<'a> Emitter<'a> {
            source,
            instructions: Vec::new(),
            constants: Vec::new(),
+            jumps: Vec::new(),
            children: Vec::new(),
        }
    }
@@ -249,6 +251,36 @@ impl<'a> Emitter<'a> {

    fn statement(&mut self, statement: &Stmt, symbols: &SymbolTable) -> Result<(), Diagnostic> {
        match &statement.kind {
+            StmtKind::If(branch) => {
+                self.expression(&branch.condition)?;
+                let conditional = self.instructions.len();
+                self.emit(Opcode::PopJumpIfFalse, 0)?;
+                for statement in &branch.body.statements {
+                    self.statement(statement, symbols)?;
+                }
+                let end = self.instructions.len();
+                self.emit(Opcode::JumpForward, 0)?;
+                self.jumps.push((conditional, self.instructions.len()));
+                if let Some(otherwise) = &branch.otherwise {
+                    for statement in &otherwise.statements {
+                        self.statement(statement, symbols)?;
+                    }
+                }
+                self.jumps.push((end, self.instructions.len()));
+            }
+            StmtKind::While(loop_) => {
+                let start = self.instructions.len();
+                self.expression(&loop_.condition)?;
+                let exit = self.instructions.len();
+                self.emit(Opcode::PopJumpIfFalse, 0)?;
+                for statement in &loop_.body.statements {
+                    self.statement(statement, symbols)?;
+                }
+                let back = self.instructions.len();
+                self.emit(Opcode::JumpBackward, 0)?;
+                self.jumps.push((back, start));
+                self.jumps.push((exit, self.instructions.len()));
+            }
            StmtKind::Binding(binding) => self.store_binding(&binding.name.text, &binding.value)?,
            StmtKind::Assignment(assignment) => {
                self.store_binding(&assignment.name.text, &assignment.value)?
@@ -308,22 +340,38 @@ impl<'a> Emitter<'a> {
                self.expression(object)?;
                self.emit(Opcode::LoadAttr, self.name_index(&name.text))?;
            }
-            ExprKind::Unary { .. } => {
-                // Literal sign folding preserves arbitrarily large integers
-                // and decimal spelling; this is not general numeric arithmetic.
-                let Some(spelling) = signed_literal(expression, false) else {
-                    return Err(error(
-                        expression.span,
-                        "numeric unary operations are not implemented; only signed number literals are supported",
-                    ));
-                };
-                self.number(&spelling, expression.span)?;
+            ExprKind::Unary { operand, .. } => {
+                if let Some(spelling) = signed_literal(expression, false) {
+                    self.number(&spelling, expression.span)?;
+                } else {
+                    self.expression(operand)?;
+                    self.simple(Opcode::UnaryNegate);
+                }
            }
-            ExprKind::Binary { .. } => {
-                return Err(error(
-                    expression.span,
-                    "numeric arithmetic bytecode is not implemented yet",
-                ));
+            ExprKind::Binary {
+                operation,
+                left,
+                right,
+            } => {
+                self.expression(left)?;
+                self.expression(right)?;
+                match operation {
+                    BinaryOp::Add => self.emit(Opcode::BinaryArithmetic, 0)?,
+                    BinaryOp::Subtract => self.emit(Opcode::BinaryArithmetic, 1)?,
+                    BinaryOp::Multiply => self.emit(Opcode::BinaryArithmetic, 2)?,
+                    BinaryOp::Divide => self.emit(Opcode::BinaryArithmetic, 3)?,
+                    _ => self
+                        .instructions
+                        .push(Instruction::compare(match operation {
+                            BinaryOp::Equal => endor_core::CompareOp::Eq,
+                            BinaryOp::NotEqual => endor_core::CompareOp::Ne,
+                            BinaryOp::Less => endor_core::CompareOp::Lt,
+                            BinaryOp::LessEqual => endor_core::CompareOp::Le,
+                            BinaryOp::Greater => endor_core::CompareOp::Gt,
+                            BinaryOp::GreaterEqual => endor_core::CompareOp::Ge,
+                            _ => unreachable!(),
+                        })),
+                }
            }
            ExprKind::Symbol(_) => {
                return Err(error(
@@ -345,7 +393,42 @@ impl<'a> Emitter<'a> {
        self.constant(Value::Number(value))
    }

-    fn finish(self) -> Result<CompiledCode, Diagnostic> {
+    fn finish(mut self) -> Result<CompiledCode, Diagnostic> {
+        // Labels refer to logical instructions. Resolve relative code-unit
+        // offsets after EXTENDED_ARG expansion, to a fixed point.
+        for attempt in 0..64 {
+            let mut offsets = vec![0_usize];
+            for i in &self.instructions {
+                let units = if i.argument <= 0xff {
+                    1
+                } else if i.argument <= 0xffff {
+                    2
+                } else if i.argument <= 0xffffff {
+                    3
+                } else {
+                    4
+                };
+                offsets.push(offsets.last().unwrap() + units);
+            }
+            let mut changed = false;
+            for &(index, target) in &self.jumps {
+                let distance = if self.instructions[index].opcode == Opcode::JumpBackward {
+                    offsets[index + 1] - offsets[target]
+                } else {
+                    offsets[target] - offsets[index + 1]
+                };
+                let operand = u32::try_from(distance)
+                    .map_err(|_| error(self.scope.span, "jump exceeds u32"))?;
+                changed |= self.instructions[index].argument != operand;
+                self.instructions[index].argument = operand;
+            }
+            if !changed {
+                break;
+            }
+            if attempt == 63 {
+                return Err(error(self.scope.span, "jump layout did not converge"));
+            }
+        }
        let line = self
            .scope
            .span
@@ -262,11 +262,22 @@ fn declared_field_checks_cover_construction_inheritance_writes_and_gc() {
        r#"
 class Base { count: Number }
 class Child: Base { label: String }
-value = Child(9, "ok")
 class Holder { child: Base }
-holder = Holder(value)
 class Unknown { value: Missing }
 "#,
+        ParseMode::Module,
+    );
+    // Interactive intentionally accepts one complete statement per source unit.
+    execute(
+        &mut vm,
+        globals,
+        r#"value = Child(9, "ok")"#,
+        ParseMode::Interactive,
+    );
+    execute(
+        &mut vm,
+        globals,
+        "holder = Holder(value)",
        ParseMode::Interactive,
    );
    let Value::Object(value) = vm
@@ -334,7 +345,7 @@ fn checked_fields_keep_declaring_self_type_and_can_be_opted_out() {
 class Link { next: Link }
 class Seed: Link {}
 "#,
-        ParseMode::Interactive,
+        ParseMode::Module,
    );
    // A recursive nonnullable field can be initialized by the trusted host in two steps.
    let Value::Object(link) = vm
@@ -345,18 +345,10 @@ fn extended_operands_work_for_large_local_and_constant_tables() {

 #[test]
 fn unsupported_execution_features_are_compile_errors_instead_of_fake_results() {
-    for (text, mode) in [
-        ("1 + 2", ParseMode::Expression),
-        (".title", ParseMode::Expression),
-        (
-            "function f(value: Number): Number { return -value }",
-            ParseMode::Module,
-        ),
-    ] {
-        let source = EndorReader::from_text("<unsupported>", text);
-        let error = compile_source(&source, mode, &CompileOptions::default()).unwrap_err();
-        assert_eq!(error.diagnostic.kind, DiagnosticKind::Compilation);
-    }
+    let source = EndorReader::from_text("<unsupported>", ".title");
+    let error =
+        compile_source(&source, ParseMode::Expression, &CompileOptions::default()).unwrap_err();
+    assert_eq!(error.diagnostic.kind, DiagnosticKind::Compilation);
 }

 #[test]
@@ -482,3 +474,79 @@ fn source_signatures_survive_template_load_and_enable_runtime_checks() {
    assert_eq!(vm.object_count(), baseline);
    cleanup(&mut vm, code, globals);
 }
+
+#[test]
+fn source_control_flow_and_exact_arithmetic_execute_real_bytecode() {
+    let mut vm = Vm::new().unwrap();
+    let text = "function main(): Number { i=0 total=0 while i<20 { if i<10 {total=total+i} else {total=total-i} i=i+1 } return total }";
+    let (code, globals) = module(&mut vm, &compile(text, ParseMode::Module));
+    let main = function(&vm, globals, "main");
+    let result = vm.call(main, &[]).unwrap();
+    assert_eq!(result, Value::Number((-100_i64).into()));
+    vm.release_value(result).unwrap();
+    cleanup(&mut vm, code, globals);
+    for (text, expected) in [
+        ("0.1 + 0.2 == 0.3", Value::Bool(true)),
+        (
+            "100000000000000000000 + 1 > 100000000000000000000",
+            Value::Bool(true),
+        ),
+        ("1 / 3 + 1 / 3 + 1 / 3", Value::Number(1_i64.into())),
+        ("-(2 + 3)", Value::Number((-5_i64).into())),
+    ] {
+        let code = compile(text, ParseMode::Expression).load(&mut vm).unwrap();
+        let globals = vm.new_dict().unwrap();
+        let result = vm.execute(code, globals).unwrap();
+        assert_eq!(result, expected);
+        vm.release_value(result).unwrap();
+        vm.release(code).unwrap();
+        vm.release(globals).unwrap();
+    }
+}
+
+#[test]
+fn control_flow_definite_initialization_large_jumps_and_loop_budgets() {
+    let mut body = String::from("function main(): Number { i=0 while i<2 { if i==0 {");
+    for _ in 0..300 {
+        body.push_str("i=i+0 ");
+    }
+    body.push_str("} i=i+1 } return i }");
+    let mut vm = Vm::new().unwrap();
+    let (code, globals) = module(&mut vm, &compile(&body, ParseMode::Module));
+    let result = vm.call(function(&vm, globals, "main"), &[]).unwrap();
+    assert_eq!(result, Value::Number(2_i64.into()));
+    vm.release_value(result).unwrap();
+    cleanup(&mut vm, code, globals);
+    for text in [
+        "function f(): Number { if 1 {x=2} return x }",
+        "function f(): Number {while 0 {x=2} return x}",
+    ] {
+        assert!(
+            compile_source(
+                &EndorReader::from_text("<test>", text),
+                ParseMode::Module,
+                &CompileOptions::default()
+            )
+            .is_err()
+        );
+    }
+    let (code, globals) = module(
+        &mut vm,
+        &compile(
+            "function main(): Unit { while 1 { value=2 } }",
+            ParseMode::Module,
+        ),
+    );
+    assert!(matches!(
+        vm.call_with_limits(
+            function(&vm, globals, "main"),
+            &[],
+            ExecutionLimits {
+                max_frames: 10,
+                max_instructions: 100
+            }
+        ),
+        Err(VmError::ExecutionLimit("instructions"))
+    ));
+    cleanup(&mut vm, code, globals);
+}
@@ -901,14 +901,38 @@ impl Vm {
        })
    }

+    fn number_value<'a>(
+        &'a self,
+        value: &'a Value,
+    ) -> Result<Option<&'a crate::EndorNumber>, VmError> {
+        Ok(match value {
+            Value::Number(n) => Some(n),
+            Value::Object(o) => self
+                .object(*o)?
+                .payload()
+                .as_any()
+                .downcast_ref::<crate::EndorNumberObject>()
+                .map(|n| n.value()),
+            _ => None,
+        })
+    }
+
    fn compare_values(
        &self,
        left: &Value,
        right: &Value,
        operation: CompareOp,
    ) -> Result<bool, VmError> {
-        if matches!(left, Value::Number(_)) || matches!(right, Value::Number(_)) {
-            return Err(VmError::UnsupportedOperation("numeric comparison"));
+        let (left_number, right_number) = (self.number_value(left)?, self.number_value(right)?);
+        if let (Some(left), Some(right)) = (left_number, right_number) {
+            return left.numeric_compare(right, operation);
+        }
+        if left_number.is_some() || right_number.is_some() {
+            return match operation {
+                CompareOp::Eq => Ok(false),
+                CompareOp::Ne => Ok(true),
+                _ => Err(VmError::UnsupportedOperation("mixed numeric ordering")),
+            };
        }
        if let (Some(left), Some(right)) = (self.text_value(left)?, self.text_value(right)?) {
            return Ok(match operation {
@@ -1242,6 +1266,45 @@ impl Vm {
                        },
                    )));
                }
+                Opcode::BinaryArithmetic => {
+                    if decoded.instruction.argument == 0 {
+                        let left = Self::stack_value(frame, frame.stack.len() - 2)?;
+                        let right = Self::top_value(frame)?;
+                        if let (Value::Text(a), Value::Text(b)) = (left, right) {
+                            if a.len().saturating_add(b.len()) > 1_048_576 {
+                                return Err(VmError::InvalidArgument(
+                                    "text concatenation exceeds operation budget",
+                                ));
+                            }
+                            self.discard(frame, 2);
+                            frame.stack.push(StackEntry::Value(Value::Text(a + &b)));
+                            continue;
+                        }
+                    }
+                    let left = Self::stack_value(frame, frame.stack.len() - 2)?;
+                    let right = Self::top_value(frame)?;
+                    let left = self
+                        .number_value(&left)?
+                        .ok_or(VmError::ObjectKindMismatch("Number"))?;
+                    let right = self
+                        .number_value(&right)?
+                        .ok_or(VmError::ObjectKindMismatch("Number"))?;
+                    let result = left.arithmetic(
+                        right,
+                        crate::ArithmeticOp::from_argument(decoded.instruction.argument).unwrap(),
+                    )?;
+                    self.discard(frame, 2);
+                    frame.stack.push(StackEntry::Value(Value::Number(result)));
+                }
+                Opcode::UnaryNegate => {
+                    let value = Self::top_value(frame)?;
+                    let value = self
+                        .number_value(&value)?
+                        .ok_or(VmError::ObjectKindMismatch("Number"))?;
+                    let result = value.negated()?;
+                    self.discard(frame, 1);
+                    frame.stack.push(StackEntry::Value(Value::Number(result)));
+                }
                Opcode::CompareOp => {
                    let left = Self::stack_value(frame, frame.stack.len() - 2)?;
                    let right = Self::top_value(frame)?;
@@ -52,13 +52,13 @@ pub use objects::{
    RootTypes, TypeConstructor, TypedMethodRequirement,
 };
 pub use objects::{
-    CallArity, CallEffect, CallSignature, CallType, ChangeBatch, ChangeKey, CodeLayout, CompareOp,
-    ContextNativeFunction, DecodedInstruction, EndorBaseExceptionObject, EndorCellObject,
-    EndorCode, EndorCodeObject, EndorDecimal, EndorDictObject, EndorFunctionObject, EndorInteger,
-    EndorNativeCall, EndorNativeFunctionObject, EndorNumber, EndorNumberObject, EndorObject,
-    EndorRational, EndorReal, EndorStringObject, EndorTracebackEntry, Instruction, NativeCall,
-    NativeCallable, NativeContext, NativeFunction, NativeResult, ObjectChange, ObjectHeader,
-    ObjectPayload, ObjectRef, Opcode, ReadAccess, ReadDependency, ReadSet, Record, SourceSignature,
-    TrackedReads, Value, VmError, WeakObjectRef,
+    ArithmeticOp, CallArity, CallEffect, CallSignature, CallType, ChangeBatch, ChangeKey,
+    CodeLayout, CompareOp, ContextNativeFunction, DecodedInstruction, EndorBaseExceptionObject,
+    EndorCellObject, EndorCode, EndorCodeObject, EndorDecimal, EndorDictObject,
+    EndorFunctionObject, EndorInteger, EndorNativeCall, EndorNativeFunctionObject, EndorNumber,
+    EndorNumberObject, EndorObject, EndorRational, EndorReal, EndorStringObject,
+    EndorTracebackEntry, Instruction, NativeCall, NativeCallable, NativeContext, NativeFunction,
+    NativeResult, ObjectChange, ObjectHeader, ObjectPayload, ObjectRef, Opcode, ReadAccess,
+    ReadDependency, ReadSet, Record, SourceSignature, TrackedReads, Value, VmError, WeakObjectRef,
 };
 pub use vm::Vm;
@@ -1593,7 +1593,22 @@ fn managed_coroutine_hard_budget_accumulates_and_error_releases_frames() {
    use endor_core::CoroutineProgress;
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
-    let code = return_constant(&mut vm, Value::Nil);
+    // Reaching ReturnValue at the limit succeeds; keep a third instruction
+    // beyond the hard limit to exercise failure before the next Pending yield.
+    let code = vm
+        .new_code(
+            EndorCode::from_instructions(
+                &[
+                    Instruction::simple(Opcode::Nop),
+                    Instruction::new(Opcode::LoadConst, 0),
+                    Instruction::simple(Opcode::ReturnValue),
+                ],
+                vec![Value::Nil],
+                CodeLayout::default(),
+            )
+            .unwrap(),
+        )
+        .unwrap();
    let function = vm
        .new_function("limited", code, globals, vec![], vec![])
        .unwrap();
@@ -1603,7 +1618,9 @@ fn managed_coroutine_hard_budget_accumulates_and_error_releases_frames() {
            &[],
            ExecutionLimits {
                max_frames: 4,
-                max_instructions: 1,
+                // The second resume reaches the cumulative limit before
+                // the third instruction, without replaying the first.
+                max_instructions: 2,
            },
        )
        .unwrap();
@@ -21,12 +21,16 @@ module Endor {
    StmtKind = Binding(Binding binding)
             | Assignment(Assignment assignment)
             | MemberAssignment(MemberAssignment assignment)
+             | If(IfStatement statement)
+             | While(WhileStatement statement)
             | Return(ReturnStatement statement)
             | Expression(Expr expression)
             | Declaration(Decl declaration)
    Binding = (Name name, Expr value, span span)
    Assignment = (Name name, Expr value, span span)
    MemberAssignment = (Expr object, Name name, Expr value, span span)
+    IfStatement = (Expr condition, Block body, Block? otherwise, span span)
+    WhileStatement = (Expr condition, Block body, span span)
    ReturnStatement = (Expr? value, span span)
    InteractiveInput = (Stmt* statements, span span)

@@ -41,5 +45,5 @@ module Endor {
             | Member(Expr object, Name name)
             | Call(Expr callee, Expr* arguments)
    UnaryOp = Negate
-    BinaryOp = Add | Subtract | Multiply | Divide
+    BinaryOp = Add | Subtract | Multiply | Divide | Equal | NotEqual | Less | LessEqual | Greater | GreaterEqual
 }
@@ -1,6 +1,6 @@
 {
  "$schema": "https://json-schema.org/draft/2020-12/schema",
-  "$id": "urn:endor:ast:sha256:c7c10c6a61158810fa55044f1aa79f3558ac18ca3be59cbf7f2499b5add8df5b",
+  "$id": "urn:endor:ast:sha256:21b0349ac295d9bc8cedcad8f07d8e2d45cf220e19e7c2fad10269555fcfd71a",
  "$ref": "#/$defs/AstDocument",
  "$defs": {
    "Span": {
@@ -27,7 +27,7 @@
      "type": "object",
      "properties": {
        "schema": {
-          "const": "urn:endor:ast:sha256:c7c10c6a61158810fa55044f1aa79f3558ac18ca3be59cbf7f2499b5add8df5b"
+          "const": "urn:endor:ast:sha256:21b0349ac295d9bc8cedcad8f07d8e2d45cf220e19e7c2fad10269555fcfd71a"
        },
        "root": {
          "$ref": "#/$defs/AstRoot"
@@ -354,6 +354,38 @@
          ],
          "additionalProperties": false
        },
+        {
+          "type": "object",
+          "properties": {
+            "kind": {
+              "const": "If"
+            },
+            "data": {
+              "$ref": "#/$defs/IfStatement"
+            }
+          },
+          "required": [
+            "kind",
+            "data"
+          ],
+          "additionalProperties": false
+        },
+        {
+          "type": "object",
+          "properties": {
+            "kind": {
+              "const": "While"
+            },
+            "data": {
+              "$ref": "#/$defs/WhileStatement"
+            }
+          },
+          "required": [
+            "kind",
+            "data"
+          ],
+          "additionalProperties": false
+        },
        {
          "type": "object",
          "properties": {
@@ -468,6 +500,56 @@
      ],
      "additionalProperties": false
    },
+    "IfStatement": {
+      "type": "object",
+      "properties": {
+        "condition": {
+          "$ref": "#/$defs/Expr"
+        },
+        "body": {
+          "$ref": "#/$defs/Block"
+        },
+        "otherwise": {
+          "anyOf": [
+            {
+              "$ref": "#/$defs/Block"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
+        "span": {
+          "$ref": "#/$defs/Span"
+        }
+      },
+      "required": [
+        "condition",
+        "body",
+        "span"
+      ],
+      "additionalProperties": false
+    },
+    "WhileStatement": {
+      "type": "object",
+      "properties": {
+        "condition": {
+          "$ref": "#/$defs/Expr"
+        },
+        "body": {
+          "$ref": "#/$defs/Block"
+        },
+        "span": {
+          "$ref": "#/$defs/Span"
+        }
+      },
+      "required": [
+        "condition",
+        "body",
+        "span"
+      ],
+      "additionalProperties": false
+    },
    "ReturnStatement": {
      "type": "object",
      "properties": {
@@ -742,7 +824,13 @@
        "Add",
        "Subtract",
        "Multiply",
-        "Divide"
+        "Divide",
+        "Equal",
+        "NotEqual",
+        "Less",
+        "LessEqual",
+        "Greater",
+        "GreaterEqual"
      ]
    }
  }
@@ -1,6 +1,6 @@
 // Generated by scripts/generate_ast.py from Endor.asdl. Do not edit.

-export const AST_SCHEMA_ID = "urn:endor:ast:sha256:c7c10c6a61158810fa55044f1aa79f3558ac18ca3be59cbf7f2499b5add8df5b" as const;
+export const AST_SCHEMA_ID = "urn:endor:ast:sha256:21b0349ac295d9bc8cedcad8f07d8e2d45cf220e19e7c2fad10269555fcfd71a" as const;
 export interface Span { start: number; end: number; }
 export type AstDocument = { schema: typeof AST_SCHEMA_ID; root: AstRoot; };
 export type AstRoot = { kind: "Module"; data: Program; } | { kind: "Expression"; data: Expr; } | { kind: "Interactive"; data: InteractiveInput; };
@@ -13,16 +13,18 @@ export type Function = { name: Name; parameters: Array<Parameter>; return_type:
 export type Parameter = { name: Name; type_name: Name; span: Span; };
 export type Block = { statements: Array<Stmt>; span: Span; };
 export type Stmt = { kind: StmtKind; span: Span; };
-export type StmtKind = { kind: "Binding"; data: Binding; } | { kind: "Assignment"; data: Assignment; } | { kind: "MemberAssignment"; data: MemberAssignment; } | { kind: "Return"; data: ReturnStatement; } | { kind: "Expression"; data: Expr; } | { kind: "Declaration"; data: Decl; };
+export type StmtKind = { kind: "Binding"; data: Binding; } | { kind: "Assignment"; data: Assignment; } | { kind: "MemberAssignment"; data: MemberAssignment; } | { kind: "If"; data: IfStatement; } | { kind: "While"; data: WhileStatement; } | { kind: "Return"; data: ReturnStatement; } | { kind: "Expression"; data: Expr; } | { kind: "Declaration"; data: Decl; };
 export type Binding = { name: Name; value: Expr; span: Span; };
 export type Assignment = { name: Name; value: Expr; span: Span; };
 export type MemberAssignment = { object: Expr; name: Name; value: Expr; span: Span; };
+export type IfStatement = { condition: Expr; body: Block; otherwise?: Block | null; span: Span; };
+export type WhileStatement = { condition: Expr; body: Block; span: Span; };
 export type ReturnStatement = { value?: Expr | null; span: Span; };
 export type InteractiveInput = { statements: Array<Stmt>; span: Span; };
 export type Expr = { kind: ExprKind; span: Span; };
 export type ExprKind = { kind: "Name"; data: string; } | { kind: "Number"; data: string; } | { kind: "String"; data: string; } | { kind: "Symbol"; data: Name; } | { kind: "Await"; data: Expr; } | { kind: "Unary"; data: { operation: UnaryOp; operand: Expr; }; } | { kind: "Binary"; data: { operation: BinaryOp; left: Expr; right: Expr; }; } | { kind: "Member"; data: { object: Expr; name: Name; }; } | { kind: "Call"; data: { callee: Expr; arguments: Array<Expr>; }; };
 export type UnaryOp = "Negate";
-export type BinaryOp = "Add" | "Subtract" | "Multiply" | "Divide";
+export type BinaryOp = "Add" | "Subtract" | "Multiply" | "Divide" | "Equal" | "NotEqual" | "Less" | "LessEqual" | "Greater" | "GreaterEqual";
 export interface Visitor {
 visitSpan?(node: Span): boolean | void;
 visitAstDocument?(node: AstDocument): boolean | void;
@@ -40,6 +42,8 @@ visitStmtKind?(node: StmtKind): boolean | void;
 visitBinding?(node: Binding): boolean | void;
 visitAssignment?(node: Assignment): boolean | void;
 visitMemberAssignment?(node: MemberAssignment): boolean | void;
+visitIfStatement?(node: IfStatement): boolean | void;
+visitWhileStatement?(node: WhileStatement): boolean | void;
 visitReturnStatement?(node: ReturnStatement): boolean | void;
 visitInteractiveInput?(node: InteractiveInput): boolean | void;
 visitExpr?(node: Expr): boolean | void;
@@ -135,6 +139,12 @@ break;
 case "MemberAssignment":
 walkMemberAssignment(node.data, visitor);
 break;
+case "If":
+walkIfStatement(node.data, visitor);
+break;
+case "While":
+walkWhileStatement(node.data, visitor);
+break;
 case "Return":
 walkReturnStatement(node.data, visitor);
 break;
@@ -165,6 +175,19 @@ walkName(node.name, visitor);
 walkExpr(node.value, visitor);
 walkSpan(node.span, visitor);
 }
+export function walkIfStatement(node: IfStatement, visitor: Visitor): void {
+if (visitor.visitIfStatement?.(node) === false) return;
+walkExpr(node.condition, visitor);
+walkBlock(node.body, visitor);
+if (node.otherwise != null) walkBlock(node.otherwise, visitor);
+walkSpan(node.span, visitor);
+}
+export function walkWhileStatement(node: WhileStatement, visitor: Visitor): void {
+if (visitor.visitWhileStatement?.(node) === false) return;
+walkExpr(node.condition, visitor);
+walkBlock(node.body, visitor);
+walkSpan(node.span, visitor);
+}
 export function walkReturnStatement(node: ReturnStatement, visitor: Visitor): void {
 if (visitor.visitReturnStatement?.(node) === false) return;
 if (node.value != null) walkExpr(node.value, visitor);
@@ -3,7 +3,7 @@
 use super::Spanned;
 use crate::Span;
 pub const AST_SCHEMA_ID: &str =
-    "urn:endor:ast:sha256:c7c10c6a61158810fa55044f1aa79f3558ac18ca3be59cbf7f2499b5add8df5b";
+    "urn:endor:ast:sha256:21b0349ac295d9bc8cedcad8f07d8e2d45cf220e19e7c2fad10269555fcfd71a";
 #[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
 #[serde(deny_unknown_fields)]
 pub struct AstDocument {
@@ -141,6 +141,8 @@ pub enum StmtKind {
    Binding(Binding),
    Assignment(Assignment),
    MemberAssignment(MemberAssignment),
+    If(IfStatement),
+    While(WhileStatement),
    Return(ReturnStatement),
    Expression(Expr),
    Declaration(Decl),
@@ -151,6 +153,8 @@ impl Spanned for StmtKind {
            Self::Binding(node) => node.span(),
            Self::Assignment(node) => node.span(),
            Self::MemberAssignment(node) => node.span(),
+            Self::If(node) => node.span(),
+            Self::While(node) => node.span(),
            Self::Return(node) => node.span(),
            Self::Expression(node) => node.span(),
            Self::Declaration(node) => node.span(),
@@ -196,6 +200,31 @@ impl Spanned for MemberAssignment {
 }
 #[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
 #[serde(deny_unknown_fields)]
+pub struct IfStatement {
+    pub condition: Expr,
+    pub body: Block,
+    pub otherwise: Option<Block>,
+    pub span: Span,
+}
+impl Spanned for IfStatement {
+    fn span(&self) -> Span {
+        self.span
+    }
+}
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct WhileStatement {
+    pub condition: Expr,
+    pub body: Block,
+    pub span: Span,
+}
+impl Spanned for WhileStatement {
+    fn span(&self) -> Span {
+        self.span
+    }
+}
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[serde(deny_unknown_fields)]
 pub struct ReturnStatement {
    pub value: Option<Expr>,
    pub span: Span,
@@ -263,4 +292,10 @@ pub enum BinaryOp {
    Subtract,
    Multiply,
    Divide,
+    Equal,
+    NotEqual,
+    Less,
+    LessEqual,
+    Greater,
+    GreaterEqual,
 }
@@ -2,8 +2,8 @@

 use super::{
    Assignment, AstDocument, AstRoot, BinaryOp, Binding, Block, Class, Decl, DeclKind, Expr,
-    ExprKind, Function, InteractiveInput, MemberAssignment, Name, Parameter, Program,
-    ReturnStatement, Spanned, Stmt, StmtKind, UnaryOp,
+    ExprKind, Function, IfStatement, InteractiveInput, MemberAssignment, Name, Parameter, Program,
+    ReturnStatement, Spanned, Stmt, StmtKind, UnaryOp, WhileStatement,
 };
 use crate::Span;
 pub trait Visitor {
@@ -102,6 +102,18 @@ pub trait Visitor {
        self.leave_node();
        result
    }
+    fn visit_if_statement(&mut self, node: &IfStatement) -> Result<(), Self::Error> {
+        self.enter_node(node.span())?;
+        let result = walk_if_statement(self, node);
+        self.leave_node();
+        result
+    }
+    fn visit_while_statement(&mut self, node: &WhileStatement) -> Result<(), Self::Error> {
+        self.enter_node(node.span())?;
+        let result = walk_while_statement(self, node);
+        self.leave_node();
+        result
+    }
    fn visit_return_statement(&mut self, node: &ReturnStatement) -> Result<(), Self::Error> {
        self.enter_node(node.span())?;
        let result = walk_return_statement(self, node);
@@ -243,6 +255,12 @@ pub fn walk_stmt_kind<V: Visitor + ?Sized>(
        StmtKind::MemberAssignment(value) => {
            visitor.visit_member_assignment(value)?;
        }
+        StmtKind::If(value) => {
+            visitor.visit_if_statement(value)?;
+        }
+        StmtKind::While(value) => {
+            visitor.visit_while_statement(value)?;
+        }
        StmtKind::Return(value) => {
            visitor.visit_return_statement(value)?;
        }
@@ -280,6 +298,27 @@ pub fn walk_member_assignment<V: Visitor + ?Sized>(
    visitor.visit_span(&node.span)?;
    Ok(())
 }
+pub fn walk_if_statement<V: Visitor + ?Sized>(
+    visitor: &mut V,
+    node: &IfStatement,
+) -> Result<(), V::Error> {
+    visitor.visit_expr(&node.condition)?;
+    visitor.visit_block(&node.body)?;
+    if let Some(value) = &node.otherwise {
+        visitor.visit_block(value)?;
+    }
+    visitor.visit_span(&node.span)?;
+    Ok(())
+}
+pub fn walk_while_statement<V: Visitor + ?Sized>(
+    visitor: &mut V,
+    node: &WhileStatement,
+) -> Result<(), V::Error> {
+    visitor.visit_expr(&node.condition)?;
+    visitor.visit_block(&node.body)?;
+    visitor.visit_span(&node.span)?;
+    Ok(())
+}
 pub fn walk_return_statement<V: Visitor + ?Sized>(
    visitor: &mut V,
    node: &ReturnStatement,
@@ -78,6 +78,7 @@ peg::parser! {
            = declaration:declaration() {
                Stmt { span: declaration.span, kind: StmtKind::Declaration(declaration) }
            }
+            / control:control_statement() { control }
            / binding:binding() { binding_statement(binding) }
            / assignment:member_assignment() { assignment }
            / assignment:assignment() { assignment }
@@ -104,13 +105,25 @@ peg::parser! {
            }

        rule local_statement() -> Stmt
-            = binding:binding() { binding_statement(binding) }
+            = control:control_statement() { control }
+            / binding:binding() { binding_statement(binding) }
            / assignment:member_assignment() { assignment }
            / assignment:assignment() { assignment }
            / !return_keyword() expression:expression() {
                Stmt { span: expression.span, kind: StmtKind::Expression(expression) }
            }

+        rule control_statement() -> Stmt
+            = start:keyword("if") condition:expression() body:block()
+              otherwise:(keyword("else") body:block() { body })? {
+                let span=start.through(otherwise.as_ref().map_or(body.span,|b|b.span));
+                Stmt {span,kind:StmtKind::If(IfStatement {condition,body,otherwise,span})}
+            }
+            / start:keyword("while") condition:expression() body:block() {
+                let span=start.through(body.span);
+                Stmt {span,kind:StmtKind::While(WhileStatement {condition,body,span})}
+            }
+
        rule assignment() -> Stmt
            = name:name() equal() value:expression() {
                let span = name.span.through(value.span);
@@ -140,6 +153,13 @@ peg::parser! {
            }

        pub rule expression() -> Expr = precedence! {
+            left:(@) [Token {kind:TokenKind::EqualEqual,..}] right:@ {binary(left,BinaryOp::Equal,right)}
+            left:(@) [Token {kind:TokenKind::NotEqual,..}] right:@ {binary(left,BinaryOp::NotEqual,right)}
+            left:(@) [Token {kind:TokenKind::Less,..}] right:@ {binary(left,BinaryOp::Less,right)}
+            left:(@) [Token {kind:TokenKind::LessEqual,..}] right:@ {binary(left,BinaryOp::LessEqual,right)}
+            left:(@) [Token {kind:TokenKind::Greater,..}] right:@ {binary(left,BinaryOp::Greater,right)}
+            left:(@) [Token {kind:TokenKind::GreaterEqual,..}] right:@ {binary(left,BinaryOp::GreaterEqual,right)}
+            --
            left:(@) plus() right:@ { binary(left, BinaryOp::Add, right) }
            left:(@) minus() right:@ { binary(left, BinaryOp::Subtract, right) }
            --
@@ -59,6 +59,12 @@ peg::parser! {
            / ":" { TokenKind::Colon }
            / "," { TokenKind::Comma }
            / "." { TokenKind::Dot }
+            / "==" { TokenKind::EqualEqual }
+            / "!=" { TokenKind::NotEqual }
+            / "<=" { TokenKind::LessEqual }
+            / ">=" { TokenKind::GreaterEqual }
+            / "<" { TokenKind::Less }
+            / ">" { TokenKind::Greater }
            / "=" { TokenKind::Equal }
            / "+" { TokenKind::Plus }
            / "-" { TokenKind::Minus }
@@ -1,7 +1,7 @@
 use crate::ast::{
    Assignment, AstRoot, BinaryOp, Binding, Block, Class, Decl, DeclKind, Expr, ExprKind, Function,
-    InteractiveInput, MemberAssignment, Name, Parameter, Program, ReturnStatement, Stmt, StmtKind,
-    UnaryOp,
+    IfStatement, InteractiveInput, MemberAssignment, Name, Parameter, Program, ReturnStatement,
+    Stmt, StmtKind, UnaryOp, WhileStatement,
 };
 use crate::lexer::decode_string;
 use crate::{Diagnostic, DiagnosticKind, Span, Token, TokenKind, lex};
@@ -16,6 +16,12 @@ pub enum TokenKind {
    Comma,
    Dot,
    Equal,
+    EqualEqual,
+    NotEqual,
+    Less,
+    LessEqual,
+    Greater,
+    GreaterEqual,
    Plus,
    Minus,
    Star,
@@ -272,7 +272,7 @@ fn parser_requires_complete_input_and_rejects_unimplemented_or_malformed_syntax(
    }
    for source in [
        "", "x y", "1 +", "+1", ".5", "1.", "f(1,)", "f(,1)", "f(1 2)", "(1", "obj.", "[1]",
-        "a == b", "1.2.3",
+        "1.2.3",
    ] {
        assert!(parse_expression(source).is_err(), "{source}");
    }
@@ -7,3 +7,8 @@ license.workspace = true

 [lints]
 workspace = true
+
+[dependencies]
+num-bigint = "0.4"
+num-rational = "0.4"
+num-traits = "0.2"
@@ -258,6 +258,8 @@ pub(crate) fn read_only_opcode(opcode: Opcode) -> bool {
            | Opcode::PopJumpIfTrue
            | Opcode::ToBool
            | Opcode::UnaryNot
+            | Opcode::BinaryArithmetic
+            | Opcode::UnaryNegate
            | Opcode::CompareOp
            | Opcode::LoadDeref
            | Opcode::LoadClosure
@@ -354,6 +356,7 @@ fn verify(
            | Opcode::LoadAttr
            | Opcode::StoreAttr => index < layout.names.len(),
            Opcode::CompareOp => compare_operation(argument).is_some(),
+            Opcode::BinaryArithmetic => argument <= 3,
            Opcode::Copy => argument >= 1,
            Opcode::Swap => argument >= 2,
            Opcode::JumpForward
@@ -394,8 +397,12 @@ fn verify(
            | Opcode::StoreDeref
            | Opcode::PopJumpIfFalse
            | Opcode::PopJumpIfTrue => (1, 1, 0),
-            Opcode::ToBool | Opcode::UnaryNot | Opcode::LoadAttr | Opcode::Await => (1, 1, 1),
-            Opcode::CompareOp => (2, 2, 1),
+            Opcode::ToBool
+            | Opcode::UnaryNot
+            | Opcode::LoadAttr
+            | Opcode::Await
+            | Opcode::UnaryNegate => (1, 1, 1),
+            Opcode::CompareOp | Opcode::BinaryArithmetic => (2, 2, 1),
            Opcode::StoreAttr => (2, 2, 0),
            Opcode::Copy => (argument, 0, 1),
            Opcode::Swap => (argument, 0, 0),
@@ -36,6 +36,8 @@ pub enum Opcode {
    MakeFunction = 28,
    BuildClass = 29,
    Await = 30,
+    BinaryArithmetic = 31,
+    UnaryNegate = 32,
    ExtendedArg = 255,
 }

@@ -73,6 +75,8 @@ impl Opcode {
            28 => Self::MakeFunction,
            29 => Self::BuildClass,
            30 => Self::Await,
+            31 => Self::BinaryArithmetic,
+            32 => Self::UnaryNegate,
            255 => Self::ExtendedArg,
            _ => return None,
        })
@@ -88,6 +92,7 @@ impl Opcode {
                | Self::ToBool
                | Self::UnaryNot
                | Self::Await
+                | Self::UnaryNegate
                | Self::BuildClass
        )
    }
@@ -40,7 +40,8 @@ pub use native::{
    NativeContext, NativeResult,
 };
 pub use number::{
-    EndorDecimal, EndorInteger, EndorNumber, EndorNumberObject, EndorRational, EndorReal,
+    ArithmeticOp, EndorDecimal, EndorInteger, EndorNumber, EndorNumberObject, EndorRational,
+    EndorReal,
 };
 pub use object::{
    AwaitPoll, CompareOp, EndorNativeCall, EndorNativeFunctionObject, EndorObject, NativeCall,
@@ -1,5 +1,6 @@
 //! Lossless number representations. Arithmetic and numeric equivalence are
-//! deliberately separate from representation equality.
+//! deliberately separate from representation equality; real operations preserve
+//! exact values unless a binary-float operand explicitly selects float mode.

 use std::any::Any;
 use std::fmt;
@@ -39,7 +40,16 @@ impl EndorInteger {
    }

    pub fn to_i64(&self) -> Option<i64> {
-        self.to_string().parse().ok()
+        let magnitude = self.digits.parse::<u64>().ok()?;
+        if self.negative {
+            if magnitude == (i64::MAX as u64) + 1 {
+                Some(i64::MIN)
+            } else {
+                i64::try_from(magnitude).ok()?.checked_neg()
+            }
+        } else {
+            i64::try_from(magnitude).ok()
+        }
    }
 }

@@ -299,9 +309,12 @@ impl ObjectPayload for EndorNumberObject {
        Err(VmError::UnsupportedOperation("numeric hash"))
    }

-    fn compare(&self, other: &dyn ObjectPayload, _op: CompareOp) -> Result<Option<bool>, VmError> {
-        if other.as_any().is::<Self>() {
-            return Err(VmError::UnsupportedOperation("numeric comparison"));
+    fn compare(&self, other: &dyn ObjectPayload, op: CompareOp) -> Result<Option<bool>, VmError> {
+        if let Some(other) = other.as_any().downcast_ref::<Self>() {
+            if self.value.as_real().is_none() || other.value.as_real().is_none() {
+                return Err(VmError::UnsupportedOperation("numeric comparison"));
+            }
+            return self.value.numeric_compare(&other.value, op).map(Some);
        }
        Ok(None)
    }
@@ -318,3 +331,222 @@ fn split_sign(text: &str) -> (bool, &str) {
 fn is_digits(text: &str) -> bool {
    !text.is_empty() && text.bytes().all(|byte| byte.is_ascii_digit())
 }
+
+/// Source arithmetic is exact for integers/decimals/rationals. A binary-float
+/// operand explicitly selects IEEE floating-point arithmetic, as used by host
+/// geometry/math APIs. Complex arithmetic remains unsupported.
+#[derive(Debug, Clone, Copy)]
+pub enum ArithmeticOp {
+    Add,
+    Subtract,
+    Multiply,
+    Divide,
+}
+impl ArithmeticOp {
+    pub fn from_argument(value: u32) -> Option<Self> {
+        match value {
+            0 => Some(Self::Add),
+            1 => Some(Self::Subtract),
+            2 => Some(Self::Multiply),
+            3 => Some(Self::Divide),
+            _ => None,
+        }
+    }
+}
+impl EndorNumber {
+    pub fn negated(&self) -> Result<Self, VmError> {
+        if let Some(EndorReal::BinaryFloat(bits)) = self.as_real() {
+            return Ok(Self::Real(EndorReal::BinaryFloat(bits ^ (1_u64 << 63))));
+        }
+        Self::from(0_i64).arithmetic(self, ArithmeticOp::Subtract)
+    }
+    /// Explicit narrowing for graphics/FFI boundaries; exact values themselves
+    /// retain their representation. Non-real or non-finite values are rejected.
+    pub fn to_f64(&self) -> Result<f64, VmError> {
+        use num_traits::ToPrimitive;
+        let real = self
+            .as_real()
+            .ok_or(VmError::UnsupportedOperation("complex to float"))?;
+        let value = if let EndorReal::BinaryFloat(bits) = real {
+            f64::from_bits(*bits)
+        } else {
+            exact_real(real)?.to_f64().ok_or(VmError::InvalidArgument(
+                "number exceeds binary float range",
+            ))?
+        };
+        if !value.is_finite() {
+            return Err(VmError::InvalidArgument("non-finite float conversion"));
+        }
+        Ok(value)
+    }
+    pub fn arithmetic(&self, other: &Self, op: ArithmeticOp) -> Result<Self, VmError> {
+        if let (Some(a), Some(b)) = (self.as_i64(), other.as_i64()) {
+            let integer = match op {
+                ArithmeticOp::Add => a.checked_add(b),
+                ArithmeticOp::Subtract => a.checked_sub(b),
+                ArithmeticOp::Multiply => a.checked_mul(b),
+                ArithmeticOp::Divide => a
+                    .checked_rem(b)
+                    .filter(|&r| r == 0)
+                    .and_then(|_| a.checked_div(b)),
+            };
+            if let Some(result) = integer {
+                return Ok(Self::from(result));
+            }
+        }
+        use num_traits::{ToPrimitive, Zero};
+        let (a, b) = (
+            self.as_real()
+                .ok_or(VmError::UnsupportedOperation("complex arithmetic"))?,
+            other
+                .as_real()
+                .ok_or(VmError::UnsupportedOperation("complex arithmetic"))?,
+        );
+        if matches!(a, EndorReal::BinaryFloat(_)) || matches!(b, EndorReal::BinaryFloat(_)) {
+            let convert = |n: &EndorReal| -> Result<f64, VmError> {
+                if let EndorReal::BinaryFloat(bits) = n {
+                    Ok(f64::from_bits(*bits))
+                } else {
+                    exact_real(n)?.to_f64().ok_or(VmError::InvalidArgument(
+                        "number exceeds binary float range",
+                    ))
+                }
+            };
+            let (a, b) = (convert(a)?, convert(b)?);
+            if matches!(op, ArithmeticOp::Divide) && b == 0. {
+                return Err(VmError::InvalidArgument("division by zero"));
+            }
+            let result = match op {
+                ArithmeticOp::Add => a + b,
+                ArithmeticOp::Subtract => a - b,
+                ArithmeticOp::Multiply => a * b,
+                ArithmeticOp::Divide => a / b,
+            };
+            if !result.is_finite() {
+                return Err(VmError::InvalidArgument("non-finite arithmetic result"));
+            }
+            return Ok(Self::binary_float(result));
+        }
+        let (a, b) = (exact_real(a)?, exact_real(b)?);
+        if matches!(op, ArithmeticOp::Divide) && b.is_zero() {
+            return Err(VmError::InvalidArgument("division by zero"));
+        }
+        let result = match op {
+            ArithmeticOp::Add => a + b,
+            ArithmeticOp::Subtract => a - b,
+            ArithmeticOp::Multiply => a * b,
+            ArithmeticOp::Divide => a / b,
+        };
+        if result.numer().bits() > 16_384 || result.denom().bits() > 16_384 {
+            return Err(VmError::InvalidArgument(
+                "arithmetic result exceeds operation budget",
+            ));
+        }
+        if result.is_integer() {
+            Self::integer(&result.to_integer().to_string())
+        } else {
+            Self::rational(&result.numer().to_string(), &result.denom().to_string())
+        }
+    }
+    pub fn numeric_compare(&self, other: &Self, op: CompareOp) -> Result<bool, VmError> {
+        use std::cmp::Ordering;
+        let (a, b) = (
+            self.as_real()
+                .ok_or(VmError::UnsupportedOperation("complex comparison"))?,
+            other
+                .as_real()
+                .ok_or(VmError::UnsupportedOperation("complex comparison"))?,
+        );
+        if let (Some(a), Some(b)) = (self.as_i64(), other.as_i64()) {
+            return Ok(match op {
+                CompareOp::Eq => a == b,
+                CompareOp::Ne => a != b,
+                CompareOp::Lt => a < b,
+                CompareOp::Le => a <= b,
+                CompareOp::Gt => a > b,
+                CompareOp::Ge => a >= b,
+            });
+        }
+        // Finite binary floats compare as exact binary rationals, so a large
+        // integer never loses precision merely to answer an ordering question.
+        let order = if let (EndorReal::BinaryFloat(a), EndorReal::BinaryFloat(b)) = (a, b) {
+            f64::from_bits(*a).partial_cmp(&f64::from_bits(*b))
+        } else {
+            let nonfinite = |n: &EndorReal| match n {
+                EndorReal::BinaryFloat(bits) if !f64::from_bits(*bits).is_finite() => {
+                    Some(f64::from_bits(*bits))
+                }
+                _ => None,
+            };
+            match (nonfinite(a), nonfinite(b)) {
+                (Some(a), _) if a.is_nan() => None,
+                (_, Some(b)) if b.is_nan() => None,
+                (Some(a), _) => Some(if a.is_sign_positive() {
+                    Ordering::Greater
+                } else {
+                    Ordering::Less
+                }),
+                (_, Some(b)) => Some(if b.is_sign_positive() {
+                    Ordering::Less
+                } else {
+                    Ordering::Greater
+                }),
+                _ => Some(exact_real(a)?.cmp(&exact_real(b)?)),
+            }
+        };
+        Ok(match op {
+            CompareOp::Eq => order == Some(Ordering::Equal),
+            CompareOp::Ne => order != Some(Ordering::Equal),
+            CompareOp::Lt => order == Some(Ordering::Less),
+            CompareOp::Le => matches!(order, Some(Ordering::Less | Ordering::Equal)),
+            CompareOp::Gt => order == Some(Ordering::Greater),
+            CompareOp::Ge => matches!(order, Some(Ordering::Greater | Ordering::Equal)),
+        })
+    }
+}
+fn exact_real(value: &EndorReal) -> Result<num_rational::BigRational, VmError> {
+    use num_bigint::BigInt;
+    use num_rational::BigRational;
+    let integer = |s: &str| -> Result<BigInt, VmError> {
+        if s.len() > 4096 {
+            return Err(VmError::InvalidArgument(
+                "numeric operand exceeds operation budget",
+            ));
+        }
+        s.parse()
+            .map_err(|_| VmError::InvalidArgument("invalid exact number"))
+    };
+    match value {
+        EndorReal::Integer(n) => Ok(BigRational::from_integer(integer(&n.to_string())?)),
+        EndorReal::Rational(n) => Ok(BigRational::new(
+            integer(&n.numerator.to_string())?,
+            integer(&n.denominator.to_string())?,
+        )),
+        EndorReal::BinaryFloat(bits) => BigRational::from_float(f64::from_bits(*bits))
+            .ok_or(VmError::InvalidArgument("non-finite exact conversion")),
+        EndorReal::Decimal(n) => {
+            let parts: Vec<_> = n.literal.split(['e', 'E']).collect();
+            let exponent = if parts.len() == 2 {
+                parts[1].parse::<i32>().map_err(|_| {
+                    VmError::InvalidArgument("numeric exponent exceeds operation budget")
+                })?
+            } else {
+                0
+            };
+            let decimals = parts[0].split_once('.').map_or(0, |(_, s)| s.len()) as i64;
+            let power = i64::from(exponent) - decimals;
+            if power.abs() > 4096 {
+                return Err(VmError::InvalidArgument(
+                    "numeric exponent exceeds operation budget",
+                ));
+            }
+            let digits = integer(&parts[0].replace('.', ""))?;
+            let factor = BigInt::from(10).pow(power.unsigned_abs() as u32);
+            Ok(if power < 0 {
+                BigRational::new(digits, factor)
+            } else {
+                BigRational::from_integer(digits * factor)
+            })
+        }
+    }
+}
@@ -0,0 +1,58 @@
+use objects::{ArithmeticOp, CompareOp, EndorNumber, EndorReal};
+fn equal(a: &EndorNumber, b: &EndorNumber) {
+    assert!(a.numeric_compare(b, CompareOp::Eq).unwrap());
+}
+#[test]
+fn exact_real_arithmetic_keeps_large_values_and_cross_representation_equivalence() {
+    let tenth = EndorNumber::decimal("0.10").unwrap();
+    let fifth = EndorNumber::rational("2", "10").unwrap();
+    equal(
+        &tenth.arithmetic(&fifth, ArithmeticOp::Add).unwrap(),
+        &EndorNumber::decimal("0.3").unwrap(),
+    );
+    let large = EndorNumber::integer("9223372036854775807").unwrap();
+    equal(
+        &large.arithmetic(&1_i64.into(), ArithmeticOp::Add).unwrap(),
+        &EndorNumber::integer("9223372036854775808").unwrap(),
+    );
+    let min = EndorNumber::integer("-9223372036854775808").unwrap();
+    assert_eq!(min.as_i64(), Some(i64::MIN));
+    equal(
+        &min.negated().unwrap(),
+        &EndorNumber::integer("9223372036854775808").unwrap(),
+    );
+    equal(
+        &EndorNumber::rational("2", "6").unwrap(),
+        &EndorNumber::rational("1", "3").unwrap(),
+    );
+    assert!(
+        EndorNumber::integer("9007199254740993")
+            .unwrap()
+            .numeric_compare(&EndorNumber::binary_float(9007199254740992.), CompareOp::Gt)
+            .unwrap()
+    );
+}
+#[test]
+fn ieee_signed_zero_nan_and_operation_limits_are_explicit() {
+    let negative = EndorNumber::binary_float(0.).negated().unwrap();
+    assert_eq!(
+        negative.as_real(),
+        Some(&EndorReal::BinaryFloat((-0.0_f64).to_bits()))
+    );
+    let nan = EndorNumber::binary_float(f64::NAN);
+    assert!(!nan.numeric_compare(&nan, CompareOp::Eq).unwrap());
+    assert!(nan.numeric_compare(&nan, CompareOp::Ne).unwrap());
+    assert!(
+        EndorNumber::from(1_i64)
+            .arithmetic(&0_i64.into(), ArithmeticOp::Divide)
+            .is_err()
+    );
+    assert!(
+        EndorNumber::binary_float(f64::MAX)
+            .arithmetic(&2_i64.into(), ArithmeticOp::Multiply)
+            .is_err()
+    );
+    let huge = EndorNumber::decimal("1e99999999999999999").unwrap();
+    assert_eq!(huge.to_string(), "1e99999999999999999");
+    assert!(huge.arithmetic(&1_i64.into(), ArithmeticOp::Add).is_err());
+}
@@ -75,7 +75,9 @@ fn main() -> Result<(), endor_core::VmError> {

 `EndorInteger`、`EndorDecimal`、`EndorRational` 是内部表示结构，不是三种语言数字类。构造器验证输入；分数不能有零分母；十进制指数不转换为机器整数，所以不会因指数很长而溢出。构造任意大整数或精确小数时传文本；已经被宿主转换为 f64 而丢失的精度无法恢复。整数的 `as_i64` 是显式、可失败的窄化读取，不会静默截断。

-首版不实现四则运算、排序、跨表示数值相等和数值哈希。Rust 的 PartialEq / Eq 只检查表示是否相同，不能用于解释语言的 `==`：`1.0` 与 `1.00` 保留不同小数位数；`2/6` 与 `1/3` 尚未求数值等价；NaN 位模式也被保留。VM 对两个数字对象的数值比较与哈希显式报不支持。因此数字现在可以作为字典的值，暂不能作为字典键，避免先定义错误的键相等规则。没有用“全部转换 f64”的方式补齐这些操作。
+实数四则运算和六种比较已通过统一 `EndorNumber` 实现，立即值和装箱 Number 共用语义。整数、十进制与有理数走精确运算，结果为整数或约分有理数；不将它们统一转换为 f64。任一操作数为 BinaryFloat 时显式选择二进制浮点运算；混合比较则把有限浮点数看作精确二进制有理数，避免大整数在比较时丢精度。NaN 比较遵守无序语义；一元负号保留浮点负零。复数算术／比较与数值哈希仍不支持。Rust 的 PartialEq/Eq 继续比较表示，不替代语言数值相等；字典键语义未改变，数字仍不能当键。
+
+运算有单次资源预算：精确输入最多 4096 字符、十进制指数绝对值最多 4096、结果分子与分母各不超过 16384 位。超限报错但不改变原数的无损表示。除零和非有限浮点算术结果报错。`to_f64()` 是供图形／FFI 边界显式窄化的接口，不更改原数。

 这里的“各类数字”指上述五种可表示形式，不包括符号表达式、无限展开的精确 π、带单位数量、任意位宽二进制浮点等全部数学对象；这些可在未来扩展表示协议。

@@ -164,7 +164,7 @@ fn main() -> Result<(), endor_core::VmError> {

 运行错误仍返回 `VmError`。`last_traceback()` 另提供从外到内的函数名、文件、代码首行和出错指令偏移；它保存独立元数据，不保活已经清理的帧。首行是代码声明的 first_line，不是由行号表推导出的实际错误源码行。成功的新一次调用会清空旧记录。尚无语言异常对象传播、raise／try／except 或完整源码行号表。

-暂未实现：源码闭包编译、关键字／可变参数、生成器／协程、迭代器专用指令、数值算术、自动方法绑定、指令特化和 JIT。
+暂未实现：源码闭包编译、关键字／可变参数、生成器／协程、迭代器专用指令、复数算术、自动方法绑定、指令特化和 JIT。

 ## 验证

@@ -204,3 +204,10 @@ LoadAttr 对实例自有属性返回原值；缺失时沿类型父链找方法
 在独立coroutine中，Pending保持已求值的栈顶、当前帧和返回契约，返回CoroutineProgress::Waiting { awaitable, instructions }；awaitable是由暂停帧保活的借用身份。宿主等待条件满足后再次resume，仅重查同一个Await，不重放操作数表达式、前缀写入或IO请求。每次实际执行Await计入同一硬预算；宿主不应对未就绪对象反复resume来轮询。完成结果与错误沿普通执行/清理路径传播。非coroutine调用允许立即Ready的await，Pending则明确报错，不阻塞线程。调度、取消传播和循环等待检测属于宿主；本引擎不依赖Tessera Task。

 LoadGlobal按文本名字分别观察函数globals及缺失时的captured builtins，不因无关全局写入而失效。可恢复只读Complete新增dependencies，reads保留兼容保守列表；精确验证/所有权见native-calls.md。
+
+
+## 实数运算指令
+
+`BinaryArithmetic`（31，operand 0/1/2/3）消费两个 Number 并产生一个 Number，分别对应加减乘除；operand 0 也接受两个直接文本值进行有界连接（最多 1 MiB）。`UnaryNegate`（32，无 operand）保持 1 入 1 出。验证器检查算术 operand 和栈深度；两者是无外部写入的运算，已纳入保守只读证明。失败沿同一个 VM 栈清理及 traceback 路径传播。
+
+源码 if/else 和 while 使用既有条件跳转、正向跳转和回跳，不引入宿主循环。Compiler 先记录逻辑指令标签，再迭代求解 EXTENDED_ARG 展开后的 code-unit 距离，避免大分支错跳到参数前缀。每次真实循环迭代仍消耗同一累计预算并支持已有协作暂停。
@@ -26,7 +26,9 @@ CompileOptions.globals 显式声明宿主会提供的 globals／builtins 名称
 | 源结构 | 生成方式 |
 | --- | --- |
 | 字符串、整数、十进制常量 | 放入常量表并 LoadConst；数字经现有 EndorNumber 解析，不转换为 f64 |
-| 数字字面量前的一个或多个负号 | 折叠符号为精确常量；不是任意表达式的一元算术 |
+| 一元负号 | 字面量折叠保留拼写；其他表达式发出 UnaryNegate |
+| 四则运算、比较 | BinaryArithmetic / CompareOp；实数精确语义见 builtins |
+| if / else、while | 函数局部初始化按分支合流，循环可执行零次；相对跳转经过 EXTENDED_ARG 布局解析 |
 | 局部读取／let／赋值 | LoadFast／StoreFast；参数和局部名称在 CodeLayout 中 |
 | 全局读取／赋值 | LoadGlobal／StoreGlobal，使用该代码对象的 names 表 |
 | 函数声明 | 子代码模板 → LoadConst(code) → MakeFunction(0, 0) → StoreGlobal |
@@ -38,7 +40,7 @@ CompileOptions.globals 显式声明宿主会提供的 globals／builtins 名称

 源码 parser 接受绑定／名称及属性赋值／表达式语句与可选末尾带值 return；空 return 仍仅由 AST 调用方构造。模块初始化发布函数／类并返回 nil，不自动调用 main。Lyra 宿主选择入口属于宿主行为。

-二元算术、非字面量的一元负号和符号值 .name 目前产生明确 Compilation 诊断，不伪造运行结果。导入、Agent、条件／循环、关键字参数等仍未实现。函数参数个数和对象是否可调用由 VM 在运行时检查。
+符号值 .name 仍产生明确 Compilation 诊断。四则运算、一元负号、六种比较、if/else 与 while 已接入真实字节码。导入、Agent、关键字参数、布尔运算符及 break/continue 等仍未实现。函数参数个数和对象是否可调用由 VM 在运行时检查。

 ## 装载、执行与所有权

@@ -61,3 +63,5 @@ lyra run [--entry name] <file|-> 编译模块、执行初始化、调用无参


 Await表达式参与普通名称/初始化分析，先编译operand，再发出无参数Await opcode。该链路保存实际结果的栈位置，不通过回放函数实现等待；没有新增async声明或静态awaitable类型检查。语法与运行上下文见frontend及bytecode主题。
+
+控制流中的局部变量仍为函数作用域。if 两边都能到达后续语句时，仅保留两边都已初始化的名字；一边 return 时采用仍可到达路径的初始化集合。while 中新初始化的名字不能被当作循环后一定存在。循环共享正常调用、只读调用或 coroutine 的累计指令预算，不建立第二套执行器。
@@ -68,7 +68,7 @@ parameters 和调用参数列表使用逗号分隔，不接受尾随逗号。函

 符号字面量、名称与成员分别保留为独立 AST 结构。true、false、Nil 等词目前只是普通名称，没有额外的源码字面量或内建值绑定。

-use、namespace、trait、agent、完整类型语法、条件／循环、比较／布尔运算和闭包声明等尚未加入首版。当前语法可修改；扩展时同步 AST、PEG 规则、样例和测试，不将旧草案视作不可修改的 ABI。
+use、namespace、trait、agent、完整类型语法、布尔运算、break/continue和闭包声明等尚未加入首版。当前语法可修改；扩展时同步 AST、PEG 规则、样例和测试，不将旧草案视作不可修改的 ABI。

 ## 诊断和命令

@@ -76,7 +76,7 @@ use、namespace、trait、agent、完整类型语法、条件／循环、比较

 `lyra parse <file>` 与 `lyra parse -` 成功时输出 Rust Debug 格式的 AST，失败时在 stderr 输出来源／行／列和诊断并返回非零退出码；`-` 表示从 stdin 读到 EOF，不是 REPL。阅读与来源包装规则见 [阅读器](reader.md)。可用 --mode 选择 module／expression／interactive，用 --json 输出带 schema 标识的 AstDocument；普通输出为 AstRoot Debug 文本，稳定交换格式见 [AST 模型](ast.md)。命令不执行源码、不初始化 VM、不连接数据库；具体运行与本地禁测约定见 [运行](../operations/README.md) 和 [验证](../operations/validation.md)。

-当前 Compiler 将 AST 经模块／函数名称分析转换为现有字节码，再交给 VM 解释执行。这是解释器内部的编译／执行准备步骤，不要求使用者先构建程序，见 [执行与版本模型](../architecture/execution-and-versions.md)。MakeFunction 已接入源码函数编译，但解析接受的二元算术和符号值仍没有执行语义；编译器会给出明确诊断，见 [编译链路](compiler.md)。源码闭包尚未实现。解析器也不是不可信代码沙箱，当前没有通用输入大小或解析递归深度限额。
+当前 Compiler 将 AST 经模块／函数名称分析转换为现有字节码，再交给 VM 解释执行。这是解释器内部的编译／执行准备步骤，不要求使用者先构建程序，见 [执行与版本模型](../architecture/execution-and-versions.md)。MakeFunction 已接入源码函数编译，四则运算、比较和条件／循环已可执行；符号值仍会给出明确编译诊断，见 [编译链路](compiler.md)。源码闭包尚未实现。解析器也不是不可信代码沙箱，当前没有通用输入大小或解析递归深度限额。

 裸赋值 `name = expression` 创建或更新当前作用域中的名称；它不是表达式，不能链式赋值，属性目标使用独立 MemberAssignment 节点；索引目标尚不支持。`let` 仍表示声明，保留重复声明检查；名称与初始化规则见 [Compiler](compiler.md)。两种源码写法产生独立的 Binding／Assignment 节点，宿主不改写输入。

@@ -85,3 +85,20 @@ use、namespace、trait、agent、完整类型语法、条件／循环、比较


 `await expression` 解析为 ExprKind::Await(operand)，优先级与前缀负号同级，成员/调用绑定更紧；例如await task.result()等待该调用的返回对象，(await task).field先等待task。await按表达式前缀位置识别，不引入async函数声明。执行是否允许等待由调用上下文决定，见字节码VM的Await章节。
+
+
+## 条件与循环
+
+```endor
+function sum(limit: Number): Number {
+    i = 0
+    total = 0
+    while i < limit {
+        if i < 10 { total = total + i } else { total = total - i }
+        i = i + 1
+    }
+    return total
+}
+```
+
+比较包括 `== != < <= > >=`，优先级低于四则运算；比较链暂按左结合解析，不提供 Python 式链式比较。条件使用运行时真值；字面量 true/false、and/or/not、for、break/continue 和 else-if 简写暂未加入。可使用比较结果、宿主 Bool，或 0/非零数值。if/while 可出现在函数体与单条 Interactive 输入中；Module 仍只收声明，Interactive 仍只接受一个完整语句。else 接一个花括号块，嵌套 if 写在块内。