NSDecimalNumber for Euler

output

2014-12-19 12:03:03.985 Untitled[96114:507] The maximum NSDecimalNumber is 3402823669209384634633746074317682114550000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
2014-12-19 12:03:03.987 Untitled[96114:507] Making an NSDecimalNumber 1 less than that (via an NSString) will be interpreted as 3402823669209384634633746074317682114540000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

test.m

#import <Foundation/Foundation.h>

//
// I did this in CodeRunner (https://coderunnerapp.com), which is super handy for tests like this.
//

int main(int argc, char *argv[]) {
	@autoreleasepool {
		NSString *maxDecimalAsString = [NSString stringWithFormat:@"%@", [NSDecimalNumber maximumDecimalNumber]];
		NSLog(@"The maximum NSDecimalNumber is %@", maxDecimalAsString);
		//
		// max is known to be 3402823669209384634633746074317682114550000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
		// if we subtract 1...
		//
		NSString *knownMaxMinusOne = @"3402823669209384634633746074317682114549999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999";
		NSDecimalNumber *maxMinusOne = [NSDecimalNumber decimalNumberWithString:knownMaxMinusOne];
		//
		// We end up with a number that quite different. The limit here is the mantissa supports accuracy to 38 places.
		//
		NSLog(@"Making an NSDecimalNumber 1 less than that (via an NSString) will be interpreted as %@", maxMinusOne);
	}
}