CSE machine: support for StreamViz drawing arrows

src/createContext.ts

@@ -95,6 +95,8 @@ const createEmptyRuntime = () => ({
   envStepsTotal: 0,
   breakpointSteps: [],
   changepointSteps: [],
+  streamLineage: new Map<string, string[]>(),
+  streamsPointSteps: []
 });
 
 const createEmptyDebugger = () => ({
@@ -140,6 +142,8 @@ export const createEmptyContext = <T>(
     runtime: createEmptyRuntime(),
     numberOfOuterEnvironments: 1,
     prelude: null,
+    pendingStreamFnStack: [],
+    streamLineage: new Map<string, string[]>(),
     debugger: createEmptyDebugger(),
     nativeStorage: createNativeStorage(),
     executionMethod: 'auto',

src/cse-machine/closure.ts

@@ -31,6 +31,7 @@ const closureToJS = (value: Closure, context: Context) => {
         nodes: [...context.runtime.nodes],
         breakpointSteps: [...context.runtime.breakpointSteps],
         changepointSteps: [...context.runtime.changepointSteps],
+        streamsPointSteps: [...context.runtime.streamsPointSteps],
         debuggerOn: false,
       },
     };

src/cse-machine/interpreter.ts

@@ -1,5 +1,5 @@
 /**
- * This interpreter implements an explicit-control evaluator.
+ * This interpreter implements an explicit-control evaluator. 
  *
  * Heavily adapted from https://github.com/source-academy/JSpike/
  * and the legacy interpreter
@@ -60,6 +60,7 @@ import {
   declareIdentifier,
   defineVariable,
   envChanging,
+  envChangingStreams,
   getVariable,
   handleArrayCreation,
   handleRuntimeError,
@@ -359,6 +360,25 @@ export function* generateCSEMachineStateStream(
       context.runtime.changepointSteps.push(steps + 1);
     }
 
+     if (!isPrelude && envChangingStreams(command, context)) {
+      // same as !isPrelude && envChanging(command) check above
+      // but this checks if next instruction on control is a pair() function
+      // Usage: streams visualiser
+      context.runtime.streamsPointSteps.push(steps + 1)
+    }
+    const evalResult = context.runtime.stash?.peek();
+    const mostRecentControlHeight = context.pendingStreamFnStack[context.pendingStreamFnStack.length -1]?.[1]   
+
+    if(Array.isArray(evalResult) && evalResult.length == 2 && mostRecentControlHeight != undefined && context.runtime.control?.size() == parseInt(mostRecentControlHeight) - 1) {
+      const mostRecentNullaryFnId = context.pendingStreamFnStack.pop()?.[0]
+      if (mostRecentNullaryFnId != undefined){
+        if (!context.streamLineage.get(mostRecentNullaryFnId)) {
+          context.streamLineage.set(mostRecentNullaryFnId, [])
+        }
+        context.streamLineage.get(mostRecentNullaryFnId)?.push((evalResult as any).id)
+      }
+    } 
+
     control.pop();
     if (isNode(command)) {
       context.runtime.nodes.shift();
@@ -834,6 +854,13 @@ const cmdEvaluators: CommandEvaluators = {
         context.runtime.environments.unshift(func.environment);
       }
 
+      // Streams Visualisation:
+      // If CALL0, push the nullary fn to pendingStreamFnStack 
+      // (to map which nullary fn produces which pairs; for nested nullary fn)
+      if (func.node.params.length === 0) {
+        context.pendingStreamFnStack.push([func.id, context.runtime.control !== null ? context.runtime.control.size().toString() : "0"])
+      } 
+
       // Handle special case if function is simple
       if (isSimpleFunction(func.node)) {
         // Closures convert ArrowExpressionStatements to BlockStatements

src/cse-machine/utils.ts

@@ -255,6 +255,17 @@ export const envChanging = (command: ControlItem): boolean => {
   }
 };
 
+export const envChangingStreams = (command: ControlItem, context: Context): boolean => {
+  if (isInstr(command)) {
+    const evalResult = context.runtime.stash?.peek();
+    const mostRecentControlHeight = context.pendingStreamFnStack[context.pendingStreamFnStack.length - 1]?.[1]
+    if (Array.isArray(evalResult) && evalResult.length == 2 && mostRecentControlHeight != undefined && context.runtime.control?.size() == parseInt(mostRecentControlHeight) - 1) {
+      return true
+    }
+  }
+  return false
+}
+
 // TODO: This type guard does not seem to be doing what it thinks its doing
 /**
  * To determine if the function is simple.

src/types.ts

@@ -63,8 +63,14 @@ export interface Context<T = any> {
     envStepsTotal: number;
     breakpointSteps: number[];
     changepointSteps: number[];
+    streamsPointSteps: number[]
   };
 
+  // STREAM VISUALISATION
+  streamLineage: Map<string, string[]>
+
+  pendingStreamFnStack: (string[] | undefined)[]
+
   numberOfOuterEnvironments: number;
 
   prelude: string | null;

src/utils/testing/mocks.ts

@@ -61,6 +61,7 @@ export function mockRuntimeContext(): Context {
     envStepsTotal: 0,
     breakpointSteps: [],
     changepointSteps: [],
+    streamsPointSteps: []
   };
   return context;
 }