strange behavior:
(xcode 4 breakpoint screenshot)
why does this comparison yield true? I really dont get it..
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2Read this paper by Goldberg before doing any more programming involving floating point arithmetic: download.oracle.com/docs/cd/E19957-01/806-3568/…Paul R– Paul R2011-06-19 19:04:03 +00:00Commented Jun 19, 2011 at 19:04
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Are you sure you're running the debugger on a "Debug" build? If you're running it on an optimised build with debugging symbols stripped, your debugger will have a very hard time matching breakpoints to lines in your source code.Aidan Steele– Aidan Steele2011-06-20 11:21:39 +00:00Commented Jun 20, 2011 at 11:21
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1 Answer
The code seems to be working correctly,
are you sure the comparison validates true?
Quick snippet:
for(int i=0;i<10;i++){
float value = (arc4random()%100)/(float)100.0f;
NSLog(@"%f",value);
if(value < 0.01f) {
NSLog(@"YES");
} else {
NSLog(@"NO");
}
}
Output:
0.520000
NO
0.520000
NO
0.100000
NO
0.000000
YES
0.390000
NO
0.690000
NO
0.770000
NO
0.930000
NO
0.320000
NO
0.230000
NO
EDIT - Response to comment:
In my case, the breakpoints are working correctly:
3 Comments
DucatiNerd
Thanks for taking time to look into this! The strange thing is that the test seems to yield true. At least when i set a breakpoint on the return, the debugger hits it.
Anne
On my Mac everything is working properly, checkout the screenshot.
DucatiNerd
Hi Anne, thanks again for taking time to reproduce this! I also did some tests meanwhile and it seems, the comparison actually does not yield true in my case. However, if i am in debug mode and set a breakpoint on the return in my if-body, the breakpoint is hit everytime just before the function is left. I am currently not sure why this happens in xcode/obj-c but the results are correct. Thanks again for your help and your time!
