rest args

README.md

@@ -77,7 +77,7 @@ It's where Shrimp live.
 
 ## Test Status
 
-✅ **70 tests passing** covering:
+✅ **83 tests passing** covering:
 - All stack operations (PUSH, POP, DUP)
 - All arithmetic operations (ADD, SUB, MUL, DIV, MOD)
 - All comparison operations (EQ, NEQ, LT, GT, LTE, GTE)
@@ -87,6 +87,7 @@ It's where Shrimp live.
 - All array operations (MAKE_ARRAY, ARRAY_GET, ARRAY_SET, ARRAY_PUSH, ARRAY_LEN)
 - All dictionary operations (MAKE_DICT, DICT_GET, DICT_SET, DICT_HAS)
 - Function operations (MAKE_FUNCTION, CALL, TAIL_CALL, RETURN) with parameter binding
+- **Variadic functions** with positional rest parameters
 - **Tail call optimization** with unbounded recursion (10,000+ iterations without stack overflow)
 - Exception handling (PUSH_TRY, PUSH_FINALLY, POP_TRY, THROW) with nested try/finally blocks and call stack unwinding
 - Native function interop (CALL_NATIVE) with sync and async functions
@@ -97,6 +98,7 @@ It's where Shrimp live.
 - **Relative jumps**: All JUMP instructions use PC-relative offsets instead of absolute addresses, making bytecode position-independent
 - **Simple truthiness**: Only `null` and `false` are falsy (unlike JavaScript where `0`, `""`, etc. are also falsy)
 - **Short-circuiting via compiler**: No AND/OR opcodes—compilers use JUMP patterns for proper short-circuit evaluation
+- **Variadic parameters**: Functions can collect remaining positional arguments into an array using `...rest` syntax
 
 🚧 **Still TODO**:
-- Advanced function features (variadic params, kwargs, named arguments in CALL)
+- Advanced function features (kwargs, named arguments in CALL)

src/vm.ts

@@ -332,7 +332,7 @@ export class VM {
         })
         break
 
-      case OpCode.CALL:
+      case OpCode.CALL: {
         const argCount = instruction.operand as number
 
         const args: Value[] = []
@@ -355,7 +355,8 @@ export class VM {
 
         this.scope = new Scope(fn.parentScope)
 
-        for (let i = 0; i < fn.params.length; i++) {
+        const fixedParamCount = fn.variadic ? fn.params.length - 1 : fn.params.length
+        for (let i = 0; i < fixedParamCount; i++) {
           const paramName = fn.params[i]!
           const argValue = args[i]
 
@@ -372,33 +373,40 @@ export class VM {
           }
         }
 
+        if (fn.variadic) {
+          const variadicParamName = fn.params[fn.params.length - 1]!
+          const remainingArgs = args.slice(fixedParamCount)
+          this.scope.set(variadicParamName, { type: 'array', value: remainingArgs })
+        }
+
         // subtract 1 because pc was incremented
         this.pc = fn.body - 1
         break
+      }
 
-      case OpCode.TAIL_CALL:
+      case OpCode.TAIL_CALL: {
         const tailArgCount = instruction.operand as number
 
-        const tailArgs: Value[] = []
+        const args: Value[] = []
         for (let i = 0; i < tailArgCount; i++)
-          tailArgs.unshift(this.stack.pop()!)
+          args.unshift(this.stack.pop()!)
 
-        const tailFn = this.stack.pop()!
+        const fn = this.stack.pop()!
 
-        if (tailFn.type !== 'function')
+        if (fn.type !== 'function')
           throw new Error('TAIL_CALL: not a function')
 
-        this.scope = new Scope(tailFn.parentScope)
+        this.scope = new Scope(fn.parentScope)
 
-        // same logic as CALL
-        for (let i = 0; i < tailFn.params.length; i++) {
-          const paramName = tailFn.params[i]!
-          const argValue = tailArgs[i]
+        const fixedParamCount = fn.variadic ? fn.params.length - 1 : fn.params.length
+        for (let i = 0; i < fixedParamCount; i++) {
+          const paramName = fn.params[i]!
+          const argValue = args[i]
 
           if (argValue !== undefined) {
             this.scope.set(paramName, argValue)
-          } else if (tailFn.defaults[paramName] !== undefined) {
-            const defaultIdx = tailFn.defaults[paramName]!
+          } else if (fn.defaults[paramName] !== undefined) {
+            const defaultIdx = fn.defaults[paramName]!
             const defaultValue = this.constants[defaultIdx]!
             if (defaultValue.type === 'function_def')
               throw new Error('Default value cannot be a function definition')
@@ -408,9 +416,16 @@ export class VM {
           }
         }
 
+        if (fn.variadic) {
+          const variadicParamName = fn.params[fn.params.length - 1]!
+          const remainingArgs = args.slice(fixedParamCount)
+          this.scope.set(variadicParamName, { type: 'array', value: remainingArgs })
+        }
+
         // subtract 1 because PC was incremented
-        this.pc = tailFn.body - 1
+        this.pc = fn.body - 1
         break
+      }
 
       case OpCode.RETURN:
         const returnValue = this.stack.length ? this.stack.pop()! : toValue(null)

tests/functions.test.ts

@@ -58,3 +58,125 @@ test("CALL and RETURN - function with two parameters", async () => {
   const result = await new VM(bytecode).run()
   expect(result).toEqual({ type: 'number', value: 30 })
 })
+
+test("CALL - variadic function with no fixed params", async () => {
+  const bytecode = toBytecode(`
+    MAKE_FUNCTION (...args) #6
+    PUSH 1
+    PUSH 2
+    PUSH 3
+    CALL #3
+    HALT
+    LOAD args
+    RETURN
+  `)
+
+  const result = await new VM(bytecode).run()
+  expect(result).toEqual({
+    type: 'array',
+    value: [
+      { type: 'number', value: 1 },
+      { type: 'number', value: 2 },
+      { type: 'number', value: 3 }
+    ]
+  })
+})
+
+test("CALL - variadic function with one fixed param", async () => {
+  const bytecode = toBytecode(`
+    MAKE_FUNCTION (x ...rest) #6
+    PUSH 10
+    PUSH 20
+    PUSH 30
+    CALL #3
+    HALT
+    LOAD rest
+    RETURN
+  `)
+
+  const result = await new VM(bytecode).run()
+  // x should be 10, rest should be [20, 30]
+  expect(result).toEqual({
+    type: 'array',
+    value: [
+      { type: 'number', value: 20 },
+      { type: 'number', value: 30 }
+    ]
+  })
+})
+
+test("CALL - variadic function with two fixed params", async () => {
+  const bytecode = toBytecode(`
+    MAKE_FUNCTION (a b ...rest) #7
+    PUSH 1
+    PUSH 2
+    PUSH 3
+    PUSH 4
+    CALL #4
+    HALT
+    LOAD rest
+    RETURN
+  `)
+
+  const result = await new VM(bytecode).run()
+  // a=1, b=2, rest=[3, 4]
+  expect(result).toEqual({
+    type: 'array',
+    value: [
+      { type: 'number', value: 3 },
+      { type: 'number', value: 4 }
+    ]
+  })
+})
+
+test("CALL - variadic function with no extra args", async () => {
+  const bytecode = toBytecode(`
+    MAKE_FUNCTION (x ...rest) #4
+    PUSH 10
+    CALL #1
+    HALT
+    LOAD rest
+    RETURN
+  `)
+
+  const result = await new VM(bytecode).run()
+  // rest should be empty array
+  expect(result).toEqual({ type: 'array', value: [] })
+})
+
+test("CALL - variadic function with defaults on fixed params", async () => {
+  const bytecode = toBytecode(`
+    MAKE_FUNCTION (x=5 ...rest) #3
+    CALL #0
+    HALT
+    LOAD x
+    RETURN
+  `)
+
+  const result = await new VM(bytecode).run()
+  // x should use default value 5
+  expect(result).toEqual({ type: 'number', value: 5 })
+})
+
+test("TAIL_CALL - variadic function", async () => {
+  const bytecode = toBytecode(`
+    MAKE_FUNCTION (x ...rest) #6
+    PUSH 1
+    PUSH 2
+    PUSH 3
+    CALL #3
+    HALT
+    LOAD rest
+    RETURN
+  `)
+
+  const result = await new VM(bytecode).run()
+  // Should return the rest array [2, 3]
+  expect(result).toEqual({
+    type: 'array',
+    value: [
+      { type: 'number', value: 2 },
+      { type: 'number', value: 3 }
+    ]
+  })
+})