Correction for range

src/interpreter/Interpreter.cpp

@@ -109,13 +109,26 @@ Value Interpreter::executeNode(std::shared_ptr<ASTNode> node) {
 
     if (auto forNode = dynamic_pointer_cast<ForNode>(node)) {
         if (auto range = dynamic_pointer_cast<RangeNode>(forNode->iterable)) {
-            Value endVal = executeNode(range->end);
-            int end = static_cast<int>(endVal.toNumber());
+            int start = range->start ? static_cast<int>(executeNode(range->start).toNumber()) : 0;
+            int end = static_cast<int>(executeNode(range->end).toNumber());
+            int step = range->step ? static_cast<int>(executeNode(range->step).toNumber()) : 1;
 
-            for (int i = 0; i < end; i++) {
-                variables[forNode->varName] = Value(static_cast<double>(i));
-                for (const auto &stmt: forNode->body)
-                    executeNode(stmt);
+            if (step == 0) {
+                throw std::runtime_error("range() arg 3 must not be zero");
+            }
+
+            if (step > 0) {
+                for (int i = start; i < end; i += step) {
+                    variables[forNode->varName] = Value(static_cast<double>(i));
+                    for (const auto &stmt: forNode->body)
+                        executeNode(stmt);
+                }
+            } else {
+                for (int i = start; i > end; i += step) {
+                    variables[forNode->varName] = Value(static_cast<double>(i));
+                    for (const auto &stmt: forNode->body)
+                        executeNode(stmt);
+                }
             }
         }
         return Value(0.0);

src/interpreter/Node/RangeNode.h

@@ -23,9 +23,12 @@ along with this program; if not, see
 
 class RangeNode : public ASTNode {
 public:
+    std::shared_ptr<ASTNode> start;
     std::shared_ptr<ASTNode> end;
+    std::shared_ptr<ASTNode> step;
 
-    RangeNode(std::shared_ptr<ASTNode> e) : end(e) {
+    RangeNode(std::shared_ptr<ASTNode> s, std::shared_ptr<ASTNode> e, std::shared_ptr<ASTNode> st)
+        : start(s), end(e), step(st) {
     }
 };
 

src/interpreter/Parser.cpp

@@ -54,6 +54,12 @@ void Parser::skipNewlines() {
 }
 
 std::shared_ptr<ASTNode> Parser::parsePrimary() {
+    if (currentToken().type == TokenType::MINUS) {
+        advance();
+        auto operand = parsePrimary();
+        return make_shared<BinaryOpNode>(std::make_shared<NumberNode>(0), TokenType::MINUS, operand);
+    }
+
     if (currentToken().type == TokenType::NUMBER) {
         double value = stod(currentToken().value);
         advance();
@@ -75,9 +81,28 @@ std::shared_ptr<ASTNode> Parser::parsePrimary() {
     if (currentToken().type == TokenType::KEYWORD && currentToken().value == "range") {
         advance();
         expect(TokenType::LPAREN);
-        auto end = parseExpression();
+
+        std::vector<std::shared_ptr<ASTNode> > args;
+        args.push_back(parseExpression());
+        while (currentToken().type == TokenType::COMMA) {
+            advance();
+            args.push_back(parseExpression());
+        }
+
         expect(TokenType::RPAREN);
-        return std::make_shared<RangeNode>(end);
+
+        if (args.size() == 1) {
+            return std::make_shared<RangeNode>(nullptr, args[0], nullptr);
+        }
+        if (args.size() == 2) {
+            return std::make_shared<RangeNode>(args[0], args[1], nullptr);
+        }
+        if (args.size() == 3) {
+            return std::make_shared<RangeNode>(args[0], args[1], args[2]);
+        }
+
+        throw std::runtime_error("range() expects 1 to 3 arguments on line " +
+                                  std::to_string(currentToken().line));
     }
 
     if (currentToken().type == TokenType::LPAREN) {