minor improvements in env viz (#1489)

* minor improvements in env viz * linting
source-academy · Sep 17, 2023 · 5ee81dc · 5ee81dc
1 parent c9c9e88
commit 5ee81dc
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Showing 3 changed files with 14 additions and 21 deletions.
diff --git a/src/ec-evaluator/instrCreator.ts b/src/ec-evaluator/instrCreator.ts
@@ -100,11 +100,6 @@ export const envInstr = (env: Environment, srcNode: es.Node): EnvInstr => ({
   srcNode
 })
 
-export const pushUndefIfNeededInstr = (srcNode: es.Node): Instr => ({
-  instrType: InstrType.PUSH_UNDEFINED_IF_NEEDED,
-  srcNode
-})
-
 export const arrLitInstr = (arity: number, srcNode: es.Node): ArrLitInstr => ({
   instrType: InstrType.ARRAY_LITERAL,
   arity,

diff --git a/src/ec-evaluator/interpreter.ts b/src/ec-evaluator/interpreter.ts
@@ -348,7 +348,8 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
     // The no declarations case is handled by Agenda :: simplifyBlocksWithoutDeclarations, so no blockStatement node
     // without declarations should end up here.
     const next = agenda.peek()
-    if (!(next && isInstr(next) && next.instrType === InstrType.ENVIRONMENT)) {
+    // Push ENVIRONMENT instruction if needed
+    if (next && !(isInstr(next) && next.instrType === InstrType.ENVIRONMENT)) {
       agenda.push(instr.envInstr(currentEnvironment(context), command))
     }
 
@@ -680,7 +681,10 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
       if (hasContinueStatement(command.body as es.BlockStatement)) {
         agenda.push(instr.contMarkerInstr(command.srcNode))
       }
-      agenda.push(instr.pushUndefIfNeededInstr(command.srcNode)) // The loop returns undefined if the stash is empty
+      if (!valueProducing(command.body)) {
+        // if loop body is not value-producing, insert undefined expression statement
+        agenda.push(ast.identifier('undefined', command.body.loc))
+      }
       agenda.push(command.body)
       agenda.push(instr.popInstr(command.srcNode)) // Pop previous body value
     }
@@ -703,7 +707,10 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
       if (hasContinueStatement(command.body as es.BlockStatement)) {
         agenda.push(instr.contMarkerInstr(command.srcNode))
       }
-      agenda.push(instr.pushUndefIfNeededInstr(command.srcNode)) // The loop returns undefined if the stash is empty
+      if (!valueProducing(command.body)) {
+        // if loop body is not value-producing, insert undefined expression statement
+        agenda.push(ast.identifier('undefined', command.body.loc))
+      }
       agenda.push(command.body)
       agenda.push(instr.popInstr(command.srcNode)) // Pop previous body value
     }
@@ -830,7 +837,10 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
         const returnStatement = block.body[0] as es.ReturnStatement
         agenda.push(returnStatement.argument ?? ast.identifier('undefined', returnStatement.loc))
       } else {
-        agenda.push(instr.markerInstr(command.srcNode))
+        if (agenda.peek()) {
+          // push marker if agenda not empty
+          agenda.push(instr.markerInstr(command.srcNode))
+        }
         agenda.push(func.node.body)
       }
     } else if (typeof func === 'function') {
@@ -890,17 +900,6 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
     }
   },
 
-  [InstrType.PUSH_UNDEFINED_IF_NEEDED]: function (
-    command: Instr,
-    context: Context,
-    agenda: Agenda,
-    stash: Stash
-  ) {
-    if (stash.size() === 0) {
-      stash.push(undefined)
-    }
-  },
-
   [InstrType.ARRAY_LITERAL]: function (
     command: ArrLitInstr,
     context: Context,

diff --git a/src/ec-evaluator/types.ts b/src/ec-evaluator/types.ts
@@ -13,7 +13,6 @@ export enum InstrType {
   APPLICATION = 'Application',
   BRANCH = 'Branch',
   ENVIRONMENT = 'Environment',
-  PUSH_UNDEFINED_IF_NEEDED = 'PushUndefinedIfNeeded',
   ARRAY_LITERAL = 'ArrayLiteral',
   ARRAY_ACCESS = 'ArrayAccess',
   ARRAY_ASSIGNMENT = 'ArrayAssignment',