the post goes in detail. Essentially, imagine you have custom routines for your ints and floats and your language doesn't support generics. You'll have a code

the post goes in detail. Essentially, imagine you have custom routines for your ints and floats and your language doesn't support generics. You'll have a code like this if type is INT: answer = optimizedRoutineForInt(); else type is FLOAT: answer = optimizedRoutineForFloat(); This happens at run-time. There's an overhead. With generics, there's zero overhead. Your code will look something like answer = optimizedRoutine<Type>(); and if optimizedRoutine<Float> can be inlined at this site, there are no conditions or jumps in the code. The post goes in detail about how for sorting, this sort of comparison function is called so frequently it has a massive impact on performance