Prefix/Postfix Expressions

src/ast/utils/astToString.ts

@@ -9,7 +9,7 @@ import {
   ExpressionStatement,
   Literal,
   LocalVariableDeclarationStatement,
-  MethodInvocation,
+  MethodInvocation, PostfixExpression,PrefixExpression,
   ReturnStatement,
 } from '../types/blocks-and-statements';
 import {
@@ -125,6 +125,13 @@ export const astToString = (node: Node, indent: number = 0): string => {
     case "Void":
       return "void";
 
+    case "PostfixExpression":
+      const postfix = node as PostfixExpression;
+      return `${astToString(postfix.expression)}${postfix.operator}`;
+    case "PrefixExpression":
+      const prefix = node as PrefixExpression;
+      return `${prefix.operator}${astToString(prefix.expression)}`;
+
     default:
       return node.kind;
   }

src/ec-evaluator/__tests__/arithmetic.test.ts

@@ -208,6 +208,7 @@ it("evaluate LocalVariableDeclarationStatement to a complex arithmetic operation
   // TODO test env
 });
 
+
 it("evaluate FieldDeclaration to a basic arithmetic expression without brackets to enforce precedence correctly", () => {
   const programStr = `
     public class Test {
@@ -302,6 +303,7 @@ it("evaluate FieldDeclaration to a basic arithmetic expression without brackets
   // TODO test env
 });
 
+
 it("evaluate FieldDeclaration to a complex arithmetic expression without brackets to enforce precedence correctly", () => {
   const programStr = `
     public class Test {
@@ -408,6 +410,7 @@ it("evaluate FieldDeclaration to a complex arithmetic expression without bracket
     "Void", // Void
   ];
 
+
   expect(result).toEqual(undefined);
   expect((context.control as ControlStub).getTrace().map(i => getControlItemStr(i))).toEqual(expectedControlTrace);
   expect((context.stash as StashStub).getTrace().map(i => getStashItemStr(i))).toEqual(expectedStashTrace);

src/ec-evaluator/interpreter.ts

@@ -1,5 +1,6 @@
 import { cloneDeep } from "lodash";
 
+
 import { 
   Assignment,
   BinaryExpression,
@@ -16,6 +17,8 @@ import {
   ReturnStatement,
   VariableDeclarator,
   Void,
+  PrefixExpression,
+  PostfixExpression,
 } from "../ast/types/blocks-and-statements";
 import {
   ConstructorDeclaration,
@@ -413,6 +416,48 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
     control.push(command.left);
   },
 
+  PrefixExpression: (
+    command:PrefixExpression,
+    environment: Environment,
+    control: Control,
+    stash: Stash,
+  ) => {
+    const operator = command.operator;  // Prefix operator (e.g., "++" or "--")
+    const operand = command.expression;  // The variable being operated on (e.g., x)
+
+    if (operand.kind !== "ExpressionName") {
+      throw new errors.RuntimeError(
+          `Postfix operator ${operator} can only be applied to variables`
+      );
+    }
+    const binExpr = {
+      kind: "BinaryExpression",
+      operator: operator === "++" ? "+" : "-",
+      left: operand,
+      right: {
+        kind: "Literal",
+        literalType: {
+          kind: "DecimalIntegerLiteral",
+          value: "1" // This is the increment/decrement value
+        },
+        location: command.location
+      },
+      location: command.location
+    } as BinaryExpression
+
+    // Push the assignment to update the variable:
+    control.push({
+      kind: "Assignment",
+      left: operand,
+      operator: "=",
+      right: binExpr,  // Use the result of the binary operation
+      location: command.location
+    });
+
+  },
+
+
+
   [InstrType.POP]: (
     _command: Instr,
     _environment: Environment,
@@ -421,6 +466,52 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
   ) => {
     stash.pop();
   },
+
+  PostfixExpression: (
+    command: PostfixExpression,
+    _environment: Environment,
+    control: Control,
+    _stash: Stash,
+  ) => {
+    const operator = command.operator;  // Postfix operator (e.g., "++" or "--")
+    const operand = command.expression;  // The variable being operated on (e.g., x)
+    if (operand.kind !== "ExpressionName") {
+      throw new errors.RuntimeError(
+          `Postfix operator ${operator} can only be applied to variables`
+      );
+    }
+
+    control.push(instr.popInstr(operand));
+
+    const binExpr = {
+            kind: "BinaryExpression",
+            operator: operator === "++" ? "+" : "-",
+            left: operand,
+            right: {
+              kind: "Literal",
+              literalType: {
+                kind: "DecimalIntegerLiteral",
+                value: "1" // This is the increment/decrement value
+              },
+              location: command.location
+            },
+            location: command.location
+          } as BinaryExpression
+
+    // Push the assignment to update the variable:
+    control.push({
+      kind: "Assignment",
+      left: operand,
+      operator: "=",
+      right: binExpr,  // Use the result of the binary operation
+      location: command.location
+    });
+
+    control.push(operand);
+
+    // Apply the postfix operation (after using the value)
+
+  },
 
   [InstrType.ASSIGNMENT]: (
     _command: AssmtInstr,
@@ -842,3 +933,4 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
     // No post-processing required for constructor.
   },
 };
+