src/format.ts

@@ -0,0 +1,202 @@
+import type { Bytecode, Constant } from "./bytecode"
+import { OpCode } from "./opcode"
+import type { Value, FunctionDef } from "./value"
+
+/**
+ * Converts a Bytecode object back to human-readable string format.
+ * This is the inverse of toBytecode().
+ */
+export const bytecodeToString = (bytecode: Bytecode): string => {
+  const lines: string[] = []
+  const { instructions, constants, labels } = bytecode
+
+  for (let i = 0; i < instructions.length; i++) {
+    // Check if there's a label at this position
+    if (labels?.has(i)) {
+      lines.push(`.${labels.get(i)}:`)
+    }
+
+    const instr = instructions[i]!
+    const opName = OpCode[instr.op] // Get string name from enum
+
+    // Format based on whether operand exists
+    if (instr.operand === undefined) {
+      lines.push(opName)
+    } else {
+      const operandStr = formatOperand(instr.op, instr.operand, constants, labels, i)
+      lines.push(`${opName} ${operandStr}`)
+    }
+  }
+
+  return lines.join('\n')
+}
+
+/**
+ * Format an operand based on the opcode type
+ */
+const formatOperand = (
+  op: OpCode,
+  operand: number | string,
+  constants: Constant[],
+  labels: Map<number, string> | undefined,
+  currentIndex: number
+): string => {
+  // Handle string operands (variable names)
+  if (typeof operand === 'string') {
+    return operand
+  }
+
+  // Handle numeric operands based on opcode
+  switch (op) {
+    case OpCode.PUSH: {
+      // Look up constant value
+      const value = constants[operand]
+      if (!value) {
+        throw new Error(`Invalid constant index: ${operand}`)
+      }
+      return formatConstant(value)
+    }
+
+    case OpCode.MAKE_FUNCTION: {
+      // Look up function definition and format as (params) .label
+      const funcDef = constants[operand]
+      if (!funcDef || !('type' in funcDef) || funcDef.type !== 'function_def') {
+        throw new Error(`Invalid function definition at constant index: ${operand}`)
+      }
+      return formatFunctionDef(funcDef as FunctionDef, labels, constants)
+    }
+
+    case OpCode.JUMP:
+    case OpCode.JUMP_IF_FALSE:
+    case OpCode.JUMP_IF_TRUE: {
+      // Convert relative offset to absolute position
+      const targetIndex = currentIndex + 1 + operand
+      const labelName = labels?.get(targetIndex)
+      return labelName ? `.${labelName}` : `#${operand}`
+    }
+
+    case OpCode.PUSH_TRY:
+    case OpCode.PUSH_FINALLY: {
+      // These use absolute positions
+      const labelName = labels?.get(operand)
+      return labelName ? `.${labelName}` : `#${operand}`
+    }
+
+    case OpCode.MAKE_ARRAY:
+    case OpCode.MAKE_DICT:
+    case OpCode.STR_CONCAT:
+      // These are just counts
+      return `#${operand}`
+
+    default:
+      return `#${operand}`
+  }
+}
+
+/**
+ * Format a constant value (from constants pool)
+ */
+const formatConstant = (constant: Constant): string => {
+  // Handle function definitions (shouldn't happen in PUSH, but be safe)
+  if ('type' in constant && constant.type === 'function_def') {
+    return '<function_def>'
+  }
+
+  // Handle Value types
+  const value = constant as Value
+  switch (value.type) {
+    case 'null':
+      return 'null'
+
+    case 'boolean':
+      return value.value.toString()
+
+    case 'number':
+      return value.value.toString()
+
+    case 'string':
+      // Use single quotes and escape special characters
+      return `'${escapeString(value.value)}'`
+
+    case 'regex': {
+      // Format as /pattern/flags
+      const pattern = value.value.source
+      const flags = value.value.flags
+      return `/${pattern}/${flags}`
+    }
+
+    case 'array': {
+      // Format as [item1, item2, ...]
+      const items = value.value.map(formatConstant).join(', ')
+      return `[${items}]`
+    }
+
+    case 'dict': {
+      // Format as {key1: value1, key2: value2}
+      const entries = Array.from(value.value.entries())
+        .map(([k, v]) => `${k}: ${formatConstant(v)}`)
+        .join(', ')
+      return `{${entries}}`
+    }
+
+    case 'function':
+    case 'native':
+      return '<function>'
+
+    default:
+      return '<unknown>'
+  }
+}
+
+/**
+ * Escape special characters in strings for output
+ */
+const escapeString = (str: string): string => {
+  return str
+    .replace(/\\/g, '\\\\')
+    .replace(/'/g, "\\'")
+    .replace(/\n/g, '\\n')
+    .replace(/\t/g, '\\t')
+    .replace(/\r/g, '\\r')
+    .replace(/\$/g, '\\$')
+}
+
+/**
+ * Format a function definition as (params) .label
+ */
+const formatFunctionDef = (
+  funcDef: FunctionDef,
+  labels: Map<number, string> | undefined,
+  constants: Constant[]
+): string => {
+  const params: string[] = []
+
+  for (let i = 0; i < funcDef.params.length; i++) {
+    const paramName = funcDef.params[i]!
+    const defaultIndex = funcDef.defaults[paramName]
+
+    if (defaultIndex !== undefined) {
+      // Parameter has a default value
+      const defaultValue = constants[defaultIndex]
+      if (!defaultValue) {
+        throw new Error(`Invalid default value index: ${defaultIndex}`)
+      }
+      params.push(`${paramName}=${formatConstant(defaultValue)}`)
+    } else if (i === funcDef.params.length - 1 && funcDef.variadic) {
+      // Last parameter and function is variadic
+      params.push(`...${paramName}`)
+    } else if (i === funcDef.params.length - 1 && funcDef.named) {
+      // Last parameter and function accepts named args
+      params.push(`@${paramName}`)
+    } else {
+      // Regular parameter
+      params.push(paramName)
+    }
+  }
+
+  // Format body address (prefer label name if available)
+  const bodyLabel = labels?.get(funcDef.body)
+  const bodyStr = bodyLabel ? `.${bodyLabel}` : `#${funcDef.body}`
+
+  return `(${params.join(' ')}) ${bodyStr}`
+}

src/index.ts

@@ -11,3 +11,4 @@ export { type Bytecode, toBytecode, type ProgramItem } from "./bytecode"
 export { wrapNative } from "./function"
 export { type Value, toValue, toString, toNumber, fromValue, toNull } from "./value"
 export { VM } from "./vm"
+export { bytecodeToString } from "./format"

src/vm.ts

@@ -386,7 +386,7 @@ export class VM {
         const varName = instruction.operand as string
         const value = this.scope.get(varName)
 
-        if (value?.type === 'function') {
+        if (value?.type === 'function' || value?.type === 'native') {
           this.stack.push(value)
           this.stack.push(toValue(0))
           this.stack.push(toValue(0))