cosmopolitan/libc/alg/shuffle.h
Justine Tunney ea0b5d9d1c Get Cosmopolitan into releasable state
A new rollup tool now exists for flattening out the headers in a way
that works better for our purposes than cpp. A lot of the API clutter
has been removed. APIs that aren't a sure thing in terms of general
recommendation are now marked internal.

There's now a smoke test for the amalgamation archive and gigantic
header file. So we can now guarantee you can use this project on the
easiest difficulty setting without the gigantic repository.

A website is being created, which is currently a work in progress:
https://justine.storage.googleapis.com/cosmopolitan/index.html
2020-11-25 08:19:00 -08:00

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719 B
C

#ifndef COSMOPOLITAN_LIBC_RAND_SHUFFLE_H_
#define COSMOPOLITAN_LIBC_RAND_SHUFFLE_H_
#if !(__ASSEMBLER__ + __LINKER__ + 0)
#include "libc/bits/xchg.h"
/**
* Fisher-Yates shuffle.
*
* @param R is a function like rand() → ≥0
* @param A is a typed array
* @param n is the number of items in A
* @see ARRAYLEN()
*/
#define shuffle(R, A, n) \
do { \
autotype(A) Array = (A); \
for (size_t i = (n)-1; i >= 1; --i) { \
xchg(&Array[i], &Array[R() % (i + 1)]); \
} \
} while (0)
#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
#endif /* COSMOPOLITAN_LIBC_RAND_SHUFFLE_H_ */