Implements new spread instruction (#1740)

* Fixed bug in for loops

* comment removed

* Fix bugs in for loops and block exec

* Fix bugs in for loops and block exec

* Fix bugs in for loops and block exec

* Implemented spread operator

* spreadinstr

* Fix formatting issues

---------

Co-authored-by: chuckyang123 <xiangwall0926@gmail.com>

src/cse-machine/instrCreator.ts

@@ -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

@@ -21,6 +21,7 @@ import { evaluateBinaryExpression, evaluateUnaryExpression } from '../utils/oper
 import * as rttc from '../utils/rttc'
 import * as seq from '../utils/statementSeqTransform'
 import { checkProgramForUndefinedVariables } from '../validator/validator'
+import { isSchemeLanguage } from '../alt-langs/mapper'
 import Closure from './closure'
 import {
   Continuation,
@@ -43,7 +44,8 @@ import {
   Instr,
   InstrType,
   UnOpInstr,
-  WhileInstr
+  WhileInstr,
+  SpreadInstr
 } from './types'
 import {
   checkNumberOfArguments,
@@ -81,7 +83,6 @@ import {
 } from './utils'
 import { isApply, isEval, schemeEval } from './scheme-macros'
 import { Transformer } from './patterns'
-import { isSchemeLanguage } from '../alt-langs/mapper'
 import { flattenList, isList } from './macro-utils'
 
 type CmdEvaluator = (
@@ -758,6 +759,12 @@ 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)
@@ -1310,5 +1317,30 @@ 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, because spread is not allowed inside arrays
+      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/patterns.ts

@@ -5,6 +5,7 @@
 // and a final template (for the list to be transformed into).
 import { List, Pair } from '../stdlib/list'
 import { _Symbol } from '../alt-langs/scheme/scm-slang/src/stdlib/base'
+import { atomic_equals, is_number } from '../alt-langs/scheme/scm-slang/src/stdlib/core-math'
 import {
   arrayToImproperList,
   arrayToList,
@@ -14,7 +15,6 @@ import {
   isPair,
   isList
 } from './macro-utils'
-import { atomic_equals, is_number } from '../alt-langs/scheme/scm-slang/src/stdlib/core-math'
 
 // a single pattern stored within the patterns component
 // may have several transformers attributed to it.

src/cse-machine/scheme-macros.ts

@@ -4,19 +4,20 @@ import { List } from '../stdlib/list'
 import { _Symbol } from '../alt-langs/scheme/scm-slang/src/stdlib/base'
 import { is_number, SchemeNumber } from '../alt-langs/scheme/scm-slang/src/stdlib/core-math'
 import { Context } from '..'
+import { encode } from '../alt-langs/scheme/scm-slang/src'
 import { Control, Stash } from './interpreter'
 import { currentTransformers, getVariable, handleRuntimeError } from './utils'
 import { Transformer, macro_transform, match } from './patterns'
 import {
   arrayToImproperList,
   arrayToList,
   flattenImproperList,
-  isImproperList
+  isImproperList,
+  flattenList,
+  isList
 } from './macro-utils'
 import { ControlItem } from './types'
-import { encode } from '../alt-langs/scheme/scm-slang/src'
 import { popInstr } from './instrCreator'
-import { flattenList, isList } from './macro-utils'
 
 // this needs to be better but for now it's fine
 export type SchemeControlItems = List | _Symbol | SchemeNumber | boolean | string

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

@@ -6,6 +6,8 @@ import * as errors from '../errors/errors'
 import { RuntimeSourceError } from '../errors/runtimeSourceError'
 import { Chapter, type Environment, type Node, type StatementSequence, type Value } from '../types'
 import * as ast from '../utils/ast/astCreator'
+import { _Symbol } from '../alt-langs/scheme/scm-slang/src/stdlib/base'
+import { is_number } from '../alt-langs/scheme/scm-slang/src/stdlib/core-math'
 import Heap from './heap'
 import * as instr from './instrCreator'
 import { Control, Transformers } from './interpreter'
@@ -22,8 +24,6 @@ import {
 import Closure from './closure'
 import { Continuation, isCallWithCurrentContinuation } from './continuations'
 import { isApply, isEval } from './scheme-macros'
-import { _Symbol } from '../alt-langs/scheme/scm-slang/src/stdlib/base'
-import { is_number } from '../alt-langs/scheme/scm-slang/src/stdlib/core-math'
 
 /**
  * Typeguard for commands to check if they are scheme values.
@@ -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) => {