General swap method for primitive types

Question

I've searched around but nothing useful for me founded.

What is the best way to write a swap method to exchange two primitive values in ObjectiveC?

You know the primitive types have different sizes, so if we pass them through something like void *, then how can we know about their size? (maybe one extra parameter for their size?)

in C#, it could be something like this :

void Swap<T>(ref T a, ref T b)
{
    T tmp = a;
    a = b;
    b = tmp;
}

An idea could be creating a temp memory block with the same size of input types, then copying them as memory blocks with a method like memcpy or something.

But I prefer something more natural in ObjectiveC, if there is a better one.

http://stackoverflow.com/a/3982397/834998 – Greg May 28 '13 at 23:31 — Greg, May 28 '13 at 23:31
Seems it's the best solution :) thank you... – Majid May 29 '13 at 02:34 — Majid, May 29 '13 at 02:34
Use Objective-C++ and employ `std::swap`. – hamstergene Jun 10 '13 at 18:15 — hamstergene, Jun 10 '13 at 18:15

score 0 · Answer 1 · edited May 23 '17 at 12:18

0

If the type is truly a primitive, you can use the XOR swap algorithm.

x = x ^ y;
y = x ^ y;
x = x ^ y;

In a macro, this could look as follows:

#define SWAP(a, b) (a^=b;b^=a;a^=b;)

But care should always be taken with macros.

Otherwise, you can try this: https://stackoverflow.com/a/3982430/2471910

edited May 23 '17 at 12:18

Community

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answered Jun 10 '13 at 17:52

Trenin

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Right - it won't work on pointers due to the compiler. It will work on other data types of the same size (long for example). – Trenin Jun 11 '13 at 16:54

General swap method for primitive types

1 Answers1