function - What does the ## operator mean/do in this C macro? -


this question has answer here:

#define swap(t, x, y) \   { \    t safe ## x ## y; \    safe ## x ## y = x; \    x = y; \    y = safe ## x ## y; \   } while (0)

the code swaps arguments x , y of type t.

the ## (double number sign) operator concatenates 2 tokens in macro invocation (text and/or arguments) given in macro definition. read more


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