saturngod saturngod -4 years ago 138
iOS Question

What's the difference between float and double?

When I run the following code ,

NSString* s= @"10000000.01";
float f = [s floatValue];
double d = [s doubleValue];

if(f > 10000000)
NSLog(@"Over Value");
else {
NSLog(@"OK Float");

if(d > 10000000)
NSLog(@"Over value");
else {
NSLog(@"OK Double");

The response is like following.

2013-04-19 17:07:29.284 float[2991:907] OK Float
2013-04-19 17:07:29.287 float[2991:907] Over value

Why float value changed to 10000000.00 instead of 10000000.01 ?

Answer Source

float is 32-bit while double is 64-bit. A float has fewer significant digits than double.

A float value doesn't store enough to hold the 10 digits of your 10000000.01.

Also see Difference between float and double for more details. That is about C/C++ but it applies to Objective-C as well.

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