NSString floatValue issue
-
Greetings,
I need to evaluate a NSString as a float value (represented by
NSNumber object). Here is my code snippet:
----
NSString *str = @"28/5";
NSNumber *nm = [NSNumber numberWithFloat:[str floatValue]];
NSLog(@"number: %@", nm );
----
this results in:
----
number: 28.0
----
However, I was expecting 5.6 as the result. How do I achieve this ? Thanks.
- Sandeep -
On Feb 26, 2008, at 10:55 AM, C Sandeep wrote:
> Greetings,
> I need to evaluate a NSString as a float value (represented by
> NSNumber object). Here is my code snippet:
> ----
> NSString *str = @"28/5";
> NSNumber *nm = [NSNumber numberWithFloat:[str floatValue]];
> NSLog(@"number: %@", nm );
> ----
> this results in:
> ----
> number: 28.0
Right. NSNumber won't evaluate the arithmetic expression, it'll only
convert a string representation of a number, stopping when it finds
something that's not part of a number (in this case, the "/"). You'll
need to do the evaluating yourself. -
As far as I know, there is no Math expression parser buit-in Cocoa.
You will have to write your own evaluator to do this.
Le 26 févr. 08 à 18:55, C Sandeep a écrit :
> Greetings,
> I need to evaluate a NSString as a float value (represented by
> NSNumber object). Here is my code snippet:
>
> ----
> NSString *str = @"28/5";
> NSNumber *nm = [NSNumber numberWithFloat:[str floatValue]];
> NSLog(@"number: %@", nm );
> ----
>
> this results in:
>
> ----
> number: 28.0
> ----
>
> However, I was expecting 5.6 as the result. How do I achieve this ?
> Thanks.
>
> - Sandeep
>
-
On Tue, Feb 26, 2008 at 6:12 PM, Jean-Daniel Dupas
<devlists...> wrote:
> As far as I know, there is no Math expression parser buit-in Cocoa.
> You will have to write your own evaluator to do this.
Or use e.g. NSTask with 'bc' (remembering to specify a scale for bc).
Hamish -
Hi all,
Thanks for the ideas. Im using the class method to evaluate such
strings, thusly:
-(NSNumber *) getNumberFrom: (NSString *) str {
NSScanner *scanner = [NSScanner scannerWithString: str];
int numerator, denominator;
[scanner scanInt: &numerator];
[scanner scanString:@"/" intoString: NULL];
[scanner scanInt: &denominator];
float result = (float) numerator/denominator;
NSNumber *nm = [NSNumber numberWithFloat: result];
return nm;
}
- Sandeep
On Tue, Feb 26, 2008 at 1:27 PM, Hamish Allan <hamish...> wrote:
> On Tue, Feb 26, 2008 at 6:12 PM, Jean-Daniel Dupas
> <devlists...> wrote:
>
>> As far as I know, there is no Math expression parser buit-in Cocoa.
>> You will have to write your own evaluator to do this.
>
> Or use e.g. NSTask with 'bc' (remembering to specify a scale for bc).
>
> Hamish
>
-
On Feb 26, 2008, at 9:47 PM, C Sandeep wrote:
> Thanks for the ideas. Im using the class method to evaluate such
> strings, thusly:
>
> -(NSNumber *) getNumberFrom: (NSString *) str {
>
> NSScanner *scanner = [NSScanner scannerWithString: str];
> int numerator, denominator;
> [scanner scanInt: &numerator];
> [scanner scanString:@"/" intoString: NULL];
> [scanner scanInt: &denominator];
> float result = (float) numerator/denominator;
> NSNumber *nm = [NSNumber numberWithFloat: result];
>
> return nm;
> }
Unless you have very good control over the input to your function, you
should probably add better error checking:
if ([scanner scanInt: &numerator])
{
// Continue parsing
}
j o a r -
[NSString floatValue] won't evaluate expressions, only convert string
representations of numbers.
I have written a category on NSString that does evaluate expressions
however; you can find it here: http://apptree.net/parser.htm
HTH,
--------
S.O.S.
On 27/02/2008, at 4:55 AM, C Sandeep wrote:
> However, I was expecting 5.6 as the result. How do I achieve
> this ? Thanks.
>
> - Sandeep
