Objective C - how to append a number to the end of another number?

I'm wanting to append a number to the end of anoth开发者_JAVA技巧er number, example:

123 + 4

1234

Get the length of the second number, k. Multiply first number by 10^k. Add in second number.

NSInteger a = 123;
NSInteger b = 4;
NSInteger c = [[NSString stringWithFormat:@"%ld%ld", (long)a, (long)b] integerValue];

If you want to do it all numerically then @bdares is the right direction, here is one option for the missing detail (typed at terminal):

NSInteger a = 123;
NSInteger b = 4;

NSInteger ab = a * (NSInteger)pow(10.0, ceil(log10(b+1))) + b;

pow, ceil & log10 are from math.h