Skipping final bit in flip.c

[fsaad]

fast-loaded-dice-roller/src/c/flip.c

Lines 14 to 25 in 19d30ab

	static int k = 30;
	static int flip_word = 0;
	static int flip_pos = 0;
	int flip(void){
	if (flip_pos == 0) {
	flip_word = rand();
	flip_pos = k;
	}
	--flip_pos;
	return (flip_word >> flip_pos) & 1;
	}

rand() returns a random 31-bit integer packed into a 32-bit integer (whose sign bit is always zero). The positions of the extracted bits should then be 0, ..., 30. However, by setting k=30, flip_pos = k, and flip_pos --, we only ever extract bits the bits at locations 0, ..., 29.

Also the code can be made more general to determine k automatically from limits.h and RAND_MAX.

[fsaad]

The lower order bits are poor quality in C, so when bumping k=31 we should change the scan order from MSB to LSB.