c++ - Why is modulo operator necessary?

Question

I've read in a document that you can replace mod operation by logical and like this :

Instead:

int Limit = Value % Range;

You do:

int Limit = Value & (Range-1);

But compilers still generate mod instructions and my question is basically : Why do compilers don't use the most efficient approach if they work the same ?

Answer 1

Um no... that only works when Range is a power of two.

For all other values, you still need the modulus % operator.

There are also some subtle (possibly implementation-defined) differences when working with negative numbers.

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As a side note: Using the % operator is probably more readable too.