TRY_LOAD opcode

GUIDE.md

@@ -195,7 +195,8 @@ CALL
 - `DUP` - Duplicate top
 
 ### Variables
-- `LOAD <name>` - Push variable value
+- `LOAD <name>` - Push variable value (throws if not found)
+- `TRY_LOAD <name>` - Push variable value if found, otherwise push name as string (never throws)
 - `STORE <name>` - Pop and store in variable
 
 ### Arithmetic

SPEC.md

@@ -86,6 +86,11 @@ class Scope {
 2. If not found, recursively check parent
 3. If not found anywhere, throw error
 
+**Variable Resolution (TRY_LOAD)**:
+1. Check current scope's locals
+2. If not found, recursively check parent
+3. If not found anywhere, return variable name as string (no error)
+
 **Variable Assignment (STORE)**:
 1. If variable exists in current scope, update it
 2. Else if variable exists in any parent scope, update it there
@@ -146,6 +151,28 @@ type ExceptionHandler = {
 **Effect**: Store top of stack into variable (following scope chain rules)
 **Stack**: [value] → []
 
+#### TRY_LOAD
+**Operand**: Variable name (string)
+**Effect**: Push variable value onto stack if found, otherwise push variable name as string
+**Stack**: [] → [value | name]
+**Errors**: Never throws (unlike LOAD)
+
+**Behavior**:
+1. Search for variable in scope chain (current scope and all parents)
+2. If found, push the variable's value onto stack
+3. If not found, push the variable name as a string value onto stack
+
+**Use Cases**:
+- Shell-like behavior where strings don't need quotes
+
+**Example**:
+```
+PUSH 42
+STORE x
+TRY_LOAD x          ; Pushes 42 (variable exists)
+TRY_LOAD y          ; Pushes "y" (variable doesn't exist)
+```
+
 ### Arithmetic Operations
 
 All arithmetic operations pop two values, perform operation, push result as number.

src/opcode.ts

@@ -5,8 +5,9 @@ export enum OpCode {
   DUP,   // operand: none | stack: [value] → [value, value]
 
   // variables
-  LOAD,  // operand: variable name (identifier) | stack: [] → [value]
+  LOAD,     // operand: variable name (identifier) | stack: [] → [value]
-  STORE, // operand: variable name (identifier) | stack: [value] → []
+  STORE,    // operand: variable name (identifier) | stack: [value] → []
+  TRY_LOAD, // operand: variable name (identifier) | stack: [] → [value] | load a variable (if found) or a string
 
   // math (coerce to number, pop 2, push result)
   ADD,   // operand: none | stack: [a, b] → [a + b]

src/vm.ts

@@ -116,7 +116,7 @@ export class VM {
         this.stopped = true
         break
 
-      case OpCode.LOAD:
+      case OpCode.LOAD: {
         const varName = instruction.operand as string
         const value = this.scope.get(varName)
 
@@ -125,6 +125,19 @@ export class VM {
 
         this.stack.push(value)
         break
+      }
+
+      case OpCode.TRY_LOAD: {
+        const varName = instruction.operand as string
+        const value = this.scope.get(varName)
+
+        if (value === undefined)
+          this.stack.push(toValue(varName))
+        else
+          this.stack.push(value)
+
+        break
+      }
 
       case OpCode.STORE:
         const name = instruction.operand as string

tests/basic.test.ts

@@ -327,6 +327,151 @@ test("STORE and LOAD - multiple variables", async () => {
   expect(await run(toBytecode(str))).toEqual({ type: 'number', value: 30 })
 })
 
+test("TRY_LOAD - variable found", async () => {
+  const str = `
+  PUSH 100
+  STORE count
+  TRY_LOAD count
+  `
+  expect(await run(toBytecode(str))).toEqual({ type: 'number', value: 100 })
+
+  const str2 = `
+  PUSH 'Bobby'
+  STORE name
+  TRY_LOAD name
+  `
+  expect(await run(toBytecode(str2))).toEqual({ type: 'string', value: 'Bobby' })
+})
+
+test("TRY_LOAD - variable missing", async () => {
+  const str = `
+  PUSH 100
+  STORE count
+  TRY_LOAD count1
+  `
+  expect(await run(toBytecode(str))).toEqual({ type: 'string', value: 'count1' })
+
+  const str2 = `
+  PUSH 'Bobby'
+  STORE name
+  TRY_LOAD full-name
+  `
+  expect(await run(toBytecode(str2))).toEqual({ type: 'string', value: 'full-name' })
+})
+
+test("TRY_LOAD - with different value types", async () => {
+  // Array
+  const str1 = `
+  PUSH 1
+  PUSH 2
+  PUSH 3
+  MAKE_ARRAY #3
+  STORE arr
+  TRY_LOAD arr
+  `
+  const result1 = await run(toBytecode(str1))
+  expect(result1.type).toBe('array')
+
+  // Dict
+  const str2 = `
+  PUSH 'key'
+  PUSH 'value'
+  MAKE_DICT #1
+  STORE dict
+  TRY_LOAD dict
+  `
+  const result2 = await run(toBytecode(str2))
+  expect(result2.type).toBe('dict')
+
+  // Boolean
+  const str3 = `
+  PUSH true
+  STORE flag
+  TRY_LOAD flag
+  `
+  expect(await run(toBytecode(str3))).toEqual({ type: 'boolean', value: true })
+
+  // Null
+  const str4 = `
+  PUSH null
+  STORE empty
+  TRY_LOAD empty
+  `
+  expect(await run(toBytecode(str4))).toEqual({ type: 'null', value: null })
+})
+
+test("TRY_LOAD - in nested scope", async () => {
+  // Function should be able to TRY_LOAD variable from parent scope
+  const str = `
+  PUSH 42
+  STORE outer
+  MAKE_FUNCTION () .fn
+  PUSH 0
+  PUSH 0
+  CALL
+  HALT
+  .fn:
+  TRY_LOAD outer
+  RETURN
+  `
+  expect(await run(toBytecode(str))).toEqual({ type: 'number', value: 42 })
+})
+
+test("TRY_LOAD - missing variable in nested scope returns name", async () => {
+  // If variable doesn't exist in any scope, should return name as string
+  const str = `
+  PUSH 42
+  STORE outer
+  MAKE_FUNCTION () .fn
+  PUSH 0
+  PUSH 0
+  CALL
+  HALT
+  .fn:
+  TRY_LOAD inner
+  RETURN
+  `
+  expect(await run(toBytecode(str))).toEqual({ type: 'string', value: 'inner' })
+})
+
+test("TRY_LOAD - used for conditional variable existence check", async () => {
+  // Pattern: use TRY_LOAD to check if variable exists and get its value or name
+  const str = `
+  PUSH 100
+  STORE count
+  TRY_LOAD count
+  PUSH 'count'
+  EQ
+  `
+  // Variable exists, so TRY_LOAD returns 100, which != 'count'
+  expect(await run(toBytecode(str))).toEqual({ type: 'boolean', value: false })
+
+  const str2 = `
+  PUSH 100
+  STORE count
+  TRY_LOAD missing
+  PUSH 'missing'
+  EQ
+  `
+  // Variable missing, so TRY_LOAD returns 'missing', which == 'missing'
+  expect(await run(toBytecode(str2))).toEqual({ type: 'boolean', value: true })
+})
+
+test("TRY_LOAD - with function value", async () => {
+  const str = `
+  MAKE_FUNCTION () .fn
+  STORE myFunc
+  JUMP .skip
+  .fn:
+  PUSH 99
+  RETURN
+  .skip:
+  TRY_LOAD myFunc
+  `
+  const result = await run(toBytecode(str))
+  expect(result.type).toBe('function')
+})
+
 test("JUMP - relative jump forward", async () => {
   const str = `
   PUSH 1