Implemented spread operator

Author: alsonleej

src/cse-machine/instrCreator.ts

@@ -16,7 +16,7 @@ import {
   Instr,
   InstrType,
   UnOpInstr,
-  WhileInstr
+  WhileInstr,
 } from './types'
 import { Transformers } from './interpreter'
 
@@ -142,3 +142,8 @@ export const breakMarkerInstr = (srcNode: Node): Instr => ({
   instrType: InstrType.BREAK_MARKER,
   srcNode
 })
+
+export const spreadInstr = (srcNode: Node): Instr => ({
+  instrType: InstrType.SPREAD,
+  srcNode
+})

src/cse-machine/interpreter.ts

@@ -43,7 +43,9 @@ import {
   Instr,
   InstrType,
   UnOpInstr,
-  WhileInstr
+  WhileInstr,
+  SpreadInstr
+
 } from './types'
 import {
   checkNumberOfArguments,
@@ -758,6 +760,13 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
     }
   },
 
+
+  SpreadElement: function (command: es.SpreadElement, context: Context, control: Control) {
+    const arr = command.argument as es.ArrayExpression
+    control.push(instr.spreadInstr(arr))
+    control.push(arr)
+  },
+
   ArrayExpression: function (command: es.ArrayExpression, context: Context, control: Control) {
     const elems = command.elements as ContiguousArrayElements
     reverse(elems)
@@ -1273,7 +1282,7 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
     const value = stash.pop()
     const index = stash.pop()
     const array = stash.pop()
-    array[index] = value
+    array[index] = value;
     stash.push(value)
   },
 
@@ -1310,5 +1319,31 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
     }
   },
 
-  [InstrType.BREAK_MARKER]: function () {}
+  [InstrType.BREAK_MARKER]: function () {},
+
+  [InstrType.SPREAD]: function (
+    command: SpreadInstr,
+    context: Context,
+    control: Control,
+    stash: Stash
+  ) {
+
+    const array = stash.pop()
+
+    // spread array
+    for (let i = 0; i < array.length; i++) {
+      stash.push(array[i])
+    }
+
+    // update call instr above
+    const cont = control.getStack()
+    const size = control.size()
+    for (let i = size - 1; i >= 0;  i--) {
+      // guaranteed at least one call instr above
+      if ((cont[i] as AppInstr).instrType === InstrType.APPLICATION) {
+        (cont[i] as AppInstr).numOfArgs += array.length - 1;
+        break; // only the nearest call instruction above
+      }
+    }
+  }
 }

src/cse-machine/types.ts

@@ -24,7 +24,8 @@ export enum InstrType {
   CONTINUE = 'Continue',
   CONTINUE_MARKER = 'ContinueMarker',
   BREAK = 'Break',
-  BREAK_MARKER = 'BreakMarker'
+  BREAK_MARKER = 'BreakMarker',
+  SPREAD = 'Spread'
 }
 
 interface BaseInstr {
@@ -78,6 +79,10 @@ export interface ArrLitInstr extends BaseInstr {
   arity: number
 }
 
+export interface SpreadInstr extends BaseInstr {
+  symbol: es.SpreadElement
+}
+
 export type Instr =
   | BaseInstr
   | WhileInstr
@@ -86,6 +91,7 @@ export type Instr =
   | BranchInstr
   | EnvInstr
   | ArrLitInstr
+  | SpreadInstr
 
 export type ControlItem = (Node | Instr | SchemeControlItems) & {
   isEnvDependent?: boolean

src/cse-machine/utils.ts

@@ -940,6 +940,7 @@ const propertySetter: PropertySetter = new Map<string, Transformer>([
   [InstrType.APPLICATION, setToTrue],
   [InstrType.ASSIGNMENT, setToTrue],
   [InstrType.ARRAY_LITERAL, setToTrue],
+  [InstrType.SPREAD, setToFalse],
   [
     InstrType.WHILE,
     (instr: WhileInstr) => {