Faulty implementation of for loop

theSalted · Jul 1, 2024 · 997f599 · 997f599
1 parent c8a1fbc
commit 997f599
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Showing 2 changed files with 48 additions and 4 deletions.
diff --git a/Sources/Lox/Interpreter.swift b/Sources/Lox/Interpreter.swift
@@ -43,9 +43,13 @@ public final class Interpreter: StatementVisitor, ExpressionVisitor {
 
     public func visit(_ stmt: If) -> Value? {
         if determineTruthy(evaluate(stmt.condition)) {
-            execute(stmt.then)
+            if case .failure(let error) = execute(stmt.then) {
+                return .failure(error)
+            }
         } else if let `else` = stmt.else {
-            execute(`else`)
+            if case .failure(let error) = execute(`else`) {
+                return .failure(error)
+            }
         }
 
         return nil
@@ -262,7 +266,10 @@ public final class Interpreter: StatementVisitor, ExpressionVisitor {
 
     public func visit(_ stmt: While) -> Value? {
         while determineTruthy(evaluate(stmt.condition)) {
-            execute(stmt.body)
+
+            if case .failure(let error) = execute(stmt.body) {
+                return .failure(error)
+            }
         }
         return nil
     }
@@ -273,7 +280,6 @@ public final class Interpreter: StatementVisitor, ExpressionVisitor {
 }
 
 extension Interpreter {
-    @discardableResult
     private func execute(_ stmt: Statement) -> Value? {
         let value = stmt.accept(visitor: self)
         return value

diff --git a/Sources/Lox/Parser.swift b/Sources/Lox/Parser.swift
@@ -56,6 +56,7 @@ public class Parser {
     }
 
     private func statement() throws -> Statement {
+        if match(.for) { return try forStatement() }
         if match(.if) { return try ifStatement() }
         if match(.print) { return try printStatement() }
         if match(.while) { return try whileStatement() }
@@ -66,6 +67,43 @@ public class Parser {
         return try expressionStatement()
     }
 
+    private func forStatement() throws -> Statement {
+        do { try consume(.leftParenthesis) }
+        catch { throw reportError("Expect '(' after for 'for'.", token: latestToken) }
+
+        let initializer: Statement?
+        if match(.semicolon) {
+            initializer = nil
+        } else if match(.var) {
+            initializer = try variableDeclaration()
+        } else {
+            initializer = try expressionStatement()
+        }
+
+        let condition: Expression = matchLatest(.semicolon) ? Literal(value: true) : try expression()
+        do { try consume(.semicolon) }
+        catch { throw reportError("Expect ';' after loop condition.", token: latestToken) }
+
+        let increment: Expression? = matchLatest(.rightParenthesis) ? nil : try expression()
+        do { try consume(.rightParenthesis) }
+        catch { throw reportError("Expect ')' after for clauses.", token: latestToken) }
+
+        var body = try statement()
+
+        if let increment {
+            body = Block(statements: [body, Expr(expression: increment)])
+        }
+
+        body = While(condition: condition, body: body)
+
+        if let initializer {
+            body = Block(statements: [initializer, body])
+        }
+
+
+        return body
+    }
+
     private func whileStatement() throws -> Statement {
         do { try consume(.leftParenthesis) }
         catch { throw reportError("Expect '(' after 'while'.", token: latestToken) }