Find shortest rotation without branches.

bams.c

#include <stdint.h>

// you can use any precision you want
typedef uint32_t ubams;
typedef int32_t bams;

static const uint32_t erro = (sizeof(ubams) < sizeof(uint32_t));
static const uint32_t most = (ubams)~0;

static inline ubams
tobams(double x)
{
    return (x/360.0) * (most + erro);
}

static inline double
todegs(bams x)
{
    return (x/(double)(most + erro)) * 360.0;
}

static inline double 
find_rotation(double a, double b)
{
   return todegs(tobams(b) - tobams(a));
}

int 
main(void)
{
   for (uint32_t i = 0; i <= 360; i += 10) 
      printf("from %u to 350 == %.2f\n", i, find_rotation(i, 350));

   return 0;
}

native.c

#include <stdint.h>
#include <math.h>
 
static inline double
modn(double a, double b)
{
   return a - b * round(a / b);
}

static inline double 
find_rotation(double a, double b)
{
   return modn(b - a, 360);
}
 
int 
main(void)
{
   for (uint32_t i = 0; i <= 360; i += 10) 
      printf("from %u to 350 == %.2f\n", i, find_rotation(i, 350));
 
   return 0;
}