title: get zero instead of a float value-Objective C
body: <p>I have an expression from the strCal string strcal value is @"((24 - 18) / 87) * 100"
  I want to have the result correct to 4 decimal so I retrieve the result using floatValue method </p>
  
  <p>But instead of 6.8966 I get 0</p>
  
  <p>This is my code</p>
  
  <pre><code>NSString *strCal=[NSString stringWithFormat:@"   
                        ((%d%@)%@)%@",number,strMinus,strDivide,strMultiple];
      NSExpression *exp=[NSExpression expressionWithFormat:strCal];
      float result=[[exp expressionValueWithObject:nil context:nil] floatValue];
      NSLog(@"result:%f",result);
  </code></pre>
  
  <p>result:0.000000</p>