Compile to Bytecode

Lower a Program AST into stack-based bytecode.

This is the compiler step that produces a separate executable artifact. The VM will consume this bytecode later.

Function signature

func Compile(prog *Program) Bytecode

Bytecode types

Use the provided types:

• Bytecode with Main []Instr and Functions []Function
• Function with Name, Params, and Code []Instr
• Instr with Op, Int, and Str

Int is used for numeric literals, jump targets, and arity. Str is used for names and string literals.

Instruction rules

Literals / variables

• number: PUSH_NUM <int>
• string: PUSH_STR <string>
• bool: PUSH_BOOL <0|1>
• nil: PUSH_NIL
• identifier: LOAD <name>

Unary / binary

• unary -: NEG
• unary !: NOT
• + - * / == != < <= > >= map to their matching opcodes

Statements

• let / var: evaluate init (or push nil), then DEFINE_VAR <name>
• const: evaluate init, then DEFINE_CONST <name>
• assignment: evaluate expr, then STORE <name>
• expression statement: evaluate expr, then POP
• block: ENTER_SCOPE, compile statements, EXIT_SCOPE
• return: evaluate expr (or push nil), then RETURN

Control flow

• if:
  • compile condition
  • JUMP_IF_FALSE <else>
  • compile then-block
  • JUMP <end>
  • compile else-block (if any)
• while:
  • loop start label
  • compile condition
  • JUMP_IF_FALSE <end>
  • compile body
  • JUMP <start>

Jumps use absolute instruction indexes in the current code slice.

Functions

• Each function declaration becomes a Function in Bytecode.Functions.
• Function bodies are compiled like statement lists (no extra scope wrapper).
• If the last instruction is not RETURN, append PUSH_NIL + RETURN.
• Top-level statements compile into Bytecode.Main.

Notes

• Assume the AST is already valid.
• Keep the compiler readable and straightforward.

Before implementation

Use the module’s worked reconstruction and independent debugging lab to predict an intermediate artifact first. Preserve one failing counterexample while implementing the stated API. The lesson’s transfer task uses a fresh case after the guided trace.