Subtracting the count of 2 arrays and casting it to a float

main.m

NSArray *arr1 = [NSArray arrayWithObjects:@"1", @"2", nil];
NSLog(@"[arr1 count]    %lu", [arr1 count]);

NSArray *arr2 = [NSArray arrayWithObjects:@"1", @"2", @"3", nil];
NSLog(@"[arr2 count]    %lu", [arr2 count]);

float diff1 = (float) ([arr1 count] - [arr2 count]);
NSLog(@"diff1:          %f", diff1);
NSLog(@"UINT64_MAX:     %llu", UINT64_MAX);

float diff2 = (float) [arr1 count] - (float) [arr2 count];
NSLog(@"diff2:          %f", diff2);

float diff3 = (float) [arr1 count] - [arr2 count];
NSLog(@"diff3:          %f", diff3);
  
float diff4 = [arr1 count] - (float) [arr2 count];
NSLog(@"diff4:          %f", diff4);

output.txt

2012-02-06 14:29:18.842 TestApp[33956:707] [arr1 count]    2
2012-02-06 14:29:18.844 TestApp[33956:707] [arr2 count]    3
2012-02-06 14:29:18.845 TestApp[33956:707] diff1:          18446744073709551616.000000
2012-02-06 14:29:18.846 TestApp[33956:707] UINT64_MAX:     18446744073709551615
2012-02-06 14:29:18.846 TestApp[33956:707] diff2:          -1.000000
2012-02-06 14:29:18.847 TestApp[33956:707] diff3:          -1.000000
2012-02-06 14:29:18.849 TestApp[33956:707] diff4:          -1.000000