| /* origin: FreeBSD /usr/src/lib/msun/src/e_atan2f.c */ |
| /* |
| * Conversion to float by Ian Lance Taylor, Cygnus Support, [email protected]. |
| */ |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| use super::atanf; |
| use super::fabsf; |
| |
| const PI: f32 = 3.1415927410e+00; /* 0x40490fdb */ |
| const PI_LO: f32 = -8.7422776573e-08; /* 0xb3bbbd2e */ |
| |
| /// Arctangent of y/x (f32) |
| /// |
| /// Computes the inverse tangent (arc tangent) of `y/x`. |
| /// Produces the correct result even for angles near pi/2 or -pi/2 (that is, when `x` is near 0). |
| /// Returns a value in radians, in the range of -pi to pi. |
| #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
| pub fn atan2f(y: f32, x: f32) -> f32 { |
| if x.is_nan() || y.is_nan() { |
| return x + y; |
| } |
| let mut ix = x.to_bits(); |
| let mut iy = y.to_bits(); |
| |
| if ix == 0x3f800000 { |
| /* x=1.0 */ |
| return atanf(y); |
| } |
| let m = ((iy >> 31) & 1) | ((ix >> 30) & 2); /* 2*sign(x)+sign(y) */ |
| ix &= 0x7fffffff; |
| iy &= 0x7fffffff; |
| |
| /* when y = 0 */ |
| if iy == 0 { |
| return match m { |
| 0 | 1 => y, /* atan(+-0,+anything)=+-0 */ |
| 2 => PI, /* atan(+0,-anything) = pi */ |
| 3 | _ => -PI, /* atan(-0,-anything) =-pi */ |
| }; |
| } |
| /* when x = 0 */ |
| if ix == 0 { |
| return if m & 1 != 0 { -PI / 2. } else { PI / 2. }; |
| } |
| /* when x is INF */ |
| if ix == 0x7f800000 { |
| return if iy == 0x7f800000 { |
| match m { |
| 0 => PI / 4., /* atan(+INF,+INF) */ |
| 1 => -PI / 4., /* atan(-INF,+INF) */ |
| 2 => 3. * PI / 4., /* atan(+INF,-INF)*/ |
| 3 | _ => -3. * PI / 4., /* atan(-INF,-INF)*/ |
| } |
| } else { |
| match m { |
| 0 => 0., /* atan(+...,+INF) */ |
| 1 => -0., /* atan(-...,+INF) */ |
| 2 => PI, /* atan(+...,-INF) */ |
| 3 | _ => -PI, /* atan(-...,-INF) */ |
| } |
| }; |
| } |
| /* |y/x| > 0x1p26 */ |
| if (ix + (26 << 23) < iy) || (iy == 0x7f800000) { |
| return if m & 1 != 0 { -PI / 2. } else { PI / 2. }; |
| } |
| |
| /* z = atan(|y/x|) with correct underflow */ |
| let z = if (m & 2 != 0) && (iy + (26 << 23) < ix) { |
| /*|y/x| < 0x1p-26, x < 0 */ |
| 0. |
| } else { |
| atanf(fabsf(y / x)) |
| }; |
| match m { |
| 0 => z, /* atan(+,+) */ |
| 1 => -z, /* atan(-,+) */ |
| 2 => PI - (z - PI_LO), /* atan(+,-) */ |
| _ => (z - PI_LO) - PI, /* case 3 */ /* atan(-,-) */ |
| } |
| } |
