| 1 | module math |
| 2 | |
| 3 | const ( |
| 4 | modf_maxpowtwo = 4.503599627370496000e+15 |
| 5 | ) |
| 6 | |
| 7 | // modf returns integer and fractional floating-point numbers |
| 8 | // that sum to f. Both values have the same sign as f. |
| 9 | // |
| 10 | // special cases are: |
| 11 | // modf(±inf) = ±inf, nan |
| 12 | // modf(nan) = nan, nan |
| 13 | pub fn modf(f f64) (f64, f64) { |
| 14 | abs_f := abs(f) |
| 15 | mut i := 0.0 |
| 16 | if abs_f >= math.modf_maxpowtwo { |
| 17 | i = f // it must be an integer |
| 18 | } else { |
| 19 | i = abs_f + math.modf_maxpowtwo // shift fraction off right |
| 20 | i -= math.modf_maxpowtwo // shift back without fraction |
| 21 | for i > abs_f { // above arithmetic might round |
| 22 | i -= 1.0 // test again just to be sure |
| 23 | } |
| 24 | if f < 0.0 { |
| 25 | i = -i |
| 26 | } |
| 27 | } |
| 28 | return i, f - i // signed fractional part |
| 29 | } |