Claude Haiku 4.5 vs DeepSeek V4.1 Flash

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

• DeepSeek V4.1 Flash

  Passed: All 15 tests passed.

  ```javascript
  function evaluate(expression) {
    if (typeof expression !== 'string') {
      throw new Error('Expression must be a string');
    }
  
    // ---- Tokenizer ----
    const tokens = [];
    let i = 0;
    const isDigit = (c) => c >= '0' && c <= '9';
  
    while (i < expression.length) {
      const ch = expression[i];
  
      if (ch === ' ' || ch === '\t' || ch === '\n' || ch === '\r') {
        i++;
        continue;
      }
  
      if (isDigit(ch) || ch === '.') {
        const start = i;
        let dots = 0;
        while (i < expression.length && (isDigit(expression[i]) || expression[i] === '.')) {
          if (expression[i] === '.') dots++;
          i++;
        }
        const text = expression.slice(start, i);
        if (dots > 1 || text === '.') {
          throw new Error(`Invalid number '${text}'`);
        }
        tokens.push({ type: 'num', value: parseFloat(text) });
        continue;
      }
  
      if ('+-*/^()'.includes(ch)) {
        tokens.push({ type: 'op', value: ch });
        i++;
        continue;
      }
  
      throw new Error(`Invalid character '${ch}'`);
    }
  
    // ---- Parser (recursive descent) ----
    // expr   := term (('+' | '-') term)*
    // term   := unary (('*' | '/') unary)*
    // unary  := ('-' | '+') unary | power
    // power  := primary ('^' unary)?        // right-associative, tighter than unary minus
    // primary:= number | '(' expr ')'
    let pos = 0;
    const peek = () => tokens[pos];
  
    function expr() {
      let value = term();
      while (peek() && peek().type === 'op' && (peek().value === '+' || peek().value === '-')) {
        const op = tokens[pos++].value;
        const rhs = term();
        value = op === '+' ? value + rhs : value - rhs;
      }
      return value;
    }
  
    function term() {
      let value = unary();
      while (peek() && peek().type === 'op' && (peek().value === '*' || peek().value === '/')) {
        const op = tokens[pos++].value;
        const rhs = unary();
        value = op === '*' ? value * rhs : value / rhs;
      }
      return value;
    }
  
    function unary() {
      const t = peek();
      if (t && t.type === 'op' && t.value === '-') {
        pos++;
        return -unary();
      }
      if (t && t.type === 'op' && t.value === '+') {
        pos++;
        return unary();
      }
      return power();
    }
  
    function power() {
      const base = primary();
      if (peek() && peek().type === 'op' && peek().value === '^') {
        pos++;
        const exponent = unary(); // right-associative, allows unary minus after ^
        return Math.pow(base, exponent);
      }
      return base;
    }
  
    function primary() {
      const t = peek();
      if (!t) throw new Error('Unexpected end of expression');
  
      if (t.type === 'num') {
        pos++;
        return t.value;
      }
  
      if (t.type === 'op' && t.value === '(') {
        pos++;
        const value = expr();
        const closing = peek();
        if (!closing || closing.type !== 'op' || closing.value !== ')') {
          throw new Error("Expected ')'");
        }
        pos++;
        return value;
      }
  
      throw new Error(`Unexpected token '${t.value}'`);
    }
  
    const result = expr();
    if (pos !== tokens.length) {
      throw new Error(`Unexpected token '${tokens[pos].value}'`);
    }
    return result;
  }
  ```

  591 tokens in, 2,216 out (1,331 of them reasoning) · 10.4 s · $0.0028 · 1 message on Pro · answered by deepseek/deepseek-v4.1-flash via Parasail · September 27, 2026