Claude Haiku 4.5 vs Kimi K3

A hard prompt: “Evaluate an arithmetic expression, no eval”, in full.

• Claude Haiku 4.5

  Failed: 14 of 15 tests passed. First failure: evaluate("-2 ^ 2"): Expected values to be strictly deep-equal:

  ```javascript
  function evaluate(expression) {
    const tokens = tokenize(expression);
    const parser = new Parser(tokens);
    const result = parser.parseExpression();
    
    if (parser.pos !== tokens.length) {
      throw new Error("Unexpected tokens after expression");
    }
    
    return result;
  }
  
  function tokenize(expression) {
    const tokens = [];
    let i = 0;
    
    while (i < expression.length) {
      const ch = expression[i];
      
      if (/\s/.test(ch)) {
        i++;
        continue;
      }
      
      if (/\d/.test(ch)) {
        let num = '';
        while (i < expression.length && /[\d.]/.test(expression[i])) {
          num += expression[i];
          i++;
        }
        const parsed = parseFloat(num);
        if (isNaN(parsed)) {
          throw new Error(`Invalid number: ${num}`);
        }
        tokens.push({ type: 'NUMBER', value: parsed });
        continue;
      }
      
      if ('+-*/^()'.includes(ch)) {
        tokens.push({ type: ch, value: ch });
        i++;
        continue;
      }
      
      throw new Error(`Unexpected character: ${ch}`);
    }
    
    return tokens;
  }
  
  class Parser {
    constructor(tokens) {
      this.tokens = tokens;
      this.pos = 0;
    }
    
    peek() {
      return this.tokens[this.pos];
    }
    
    consume() {
      return this.tokens[this.pos++];
    }
    
    parseExpression() {
      return this.parseAddSub();
    }
    
    parseAddSub() {
      let left = this.parseMulDiv();
      
      while (this.peek() && (this.peek().type === '+' || this.peek().type === '-')) {
        const op = this.consume().type;
        const right = this.parseMulDiv();
        left = op === '+' ? left + right : left - right;
      }
      
      return left;
    }
    
    parseMulDiv() {
      let left = this.parsePower();
      
      while (this.peek() && (this.peek().type === '*' || this.peek().type === '/')) {
        const op = this.consume().type;
        const right = this.parsePower();
        left = op === '*' ? left * right : left / right;
      }
      
      return left;
    }
    
    parsePower() {
      let left = this.parseUnary();
      
      if (this.peek() && this.peek().type === '^') {
        this.consume();
        const right = this.parsePower();
        left = Math.pow(left, right);
      }
      
      return left;
    }
    
    parseUnary() {
      if (this.peek() && this.peek().type === '-') {
        this.consume();
        return -this.parseUnary();
      }
      
      if (this.peek() && this.peek().type === '+') {
        this.consume();
        return this.parseUnary();
      }
      
      return this.parsePrimary();
    }
    
    parsePrimary() {
      const token = this.peek();
      
      if (!token) {
        throw new Error("Unexpected end of expression");
      }
      
      if (token.type === 'NUMBER') {
        this.consume();
        return token.value;
      }
      
      if (token.type === '(') {
        this.consume();
        const result = this.parseExpression();
        
        if (!this.peek() || this.peek().type !== ')') {
          throw new Error("Missing closing parenthesis");
        }
        
        this.consume();
        return result;
      }
      
      throw new Error(`Unexpected token: ${token.value}`);
    }
  }
  ```

  599 tokens in, 1,007 out · 7.6 s · $0.0056 · 1 message on Pro · answered by anthropic/claude-haiku-4.5 via Amazon Bedrock · September 27, 2026

• Kimi K3

  Passed: All 15 tests passed.

  ```javascript
  function evaluate(expression) {
    if (typeof expression !== "string") {
      throw new Error("Input must be a string");
    }
  
    let pos = 0;
  
    function skipSpaces() {
      while (pos < expression.length && expression[pos] === " ") {
        pos++;
      }
    }
  
    function peek() {
      skipSpaces();
      return pos < expression.length ? expression[pos] : null;
    }
  
    function parseExpression() {
      let value = parseTerm();
      for (;;) {
        const ch = peek();
        if (ch === "+") {
          pos++;
          value += parseTerm();
        } else if (ch === "-") {
          pos++;
          value -= parseTerm();
        } else {
          return value;
        }
      }
    }
  
    function parseTerm() {
      let value = parseUnary();
      for (;;) {
        const ch = peek();
        if (ch === "*") {
          pos++;
          value *= parseUnary();
        } else if (ch === "/") {
          pos++;
          value /= parseUnary();
        } else {
          return value;
        }
      }
    }
  
    function parseUnary() {
      const ch = peek();
      if (ch === "-") {
        pos++;
        return -parseUnary();
      }
      if (ch === "+") {
        pos++;
        return parseUnary();
      }
      return parsePower();
    }
  
    function parsePower() {
      const base = parsePrimary();
      if (peek() === "^") {
        pos++;
        const exponent = parseUnary(); // right-associative, allows 2^-1
        return Math.pow(base, exponent);
      }
      return base;
    }
  
    function parsePrimary() {
      const ch = peek();
      if (ch === null) {
        throw new Error("Unexpected end of expression");
      }
      if (ch === "(") {
        pos++;
        const value = parseExpression();
        if (peek() !== ")") {
          throw new Error("Missing closing parenthesis");
        }
        pos++;
        return value;
      }
      return parseNumber();
    }
  
    function parseNumber() {
      skipSpaces();
      const start = pos;
      let sawDigit = false;
      while (pos < expression.length && expression[pos] >= "0" && expression[pos] <= "9") {
        pos++;
        sawDigit = true;
      }
      if (pos < expression.length && expression[pos] === ".") {
        pos++;
        while (pos < expression.length && expression[pos] >= "0" && expression[pos] <= "9") {
          pos++;
          sawDigit = true;
        }
      }
      if (!sawDigit) {
        throw new Error("Expected a number at position " + start);
      }
      return Number(expression.slice(start, pos));
    }
  
    const result = parseExpression();
    if (peek() !== null) {
      throw new Error("Unexpected character '" + expression[pos] + "' at position " + pos);
    }
    return result;
  }
  ```
  
  A recursive-descent parser with the precedence levels: `+`/`-` (lowest), then `*`/`/`, then unary minus, then `^` (right-associative, binds tighter than unary minus, and its exponent is parsed as unary so `2^-1` works), then numbers and parentheses. Leftover characters or missing operands throw an `Error`.

  636 tokens in, 816 out (99 of them reasoning) · 9.9 s · $0.0113 · 1 message on Pro · answered by moonshotai/kimi-k3 via Phala · September 27, 2026