std.math: add degreesToRadians and radiansToDegrees

Author: frmdstryr

lib/std/math.zig

@@ -292,6 +292,34 @@ pub inline fn tan(value: anytype) @TypeOf(value) {
     return @tan(value);
 }
 
+// Convert an angle in radians to degrees. T must be a float type.
+pub fn radiansToDegrees(comptime T: type, angle_in_radians: T) T {
+    if (@typeInfo(T) != .Float)
+        @compileError("T must be a float type.");
+    return angle_in_radians * 180.0 / pi;
+}
+
+test "radiansToDegrees" {
+    try std.testing.expectApproxEqAbs(@as(f32, 0), radiansToDegrees(f32, 0), 1e-6);
+    try std.testing.expectApproxEqAbs(@as(f32, 90), radiansToDegrees(f32, pi / 2.0), 1e-6);
+    try std.testing.expectApproxEqAbs(@as(f32, -45), radiansToDegrees(f32, -pi / 4.0), 1e-6);
+    try std.testing.expectApproxEqAbs(@as(f32, 180), radiansToDegrees(f32, pi), 1e-6);
+    try std.testing.expectApproxEqAbs(@as(f32, 360), radiansToDegrees(f32, 2.0 * pi), 1e-6);
+}
+
+// Convert an angle in degrees to radians. T must be a float type.
+pub fn degreesToRadians(comptime T: type, angle_in_degrees: T) T {
+    if (@typeInfo(T) != .Float)
+        @compileError("T must be a float type.");
+    return angle_in_degrees * pi / 180.0;
+}
+
+test "degreesToRadians" {
+    try std.testing.expectApproxEqAbs(@as(f32, pi / 2.0), degreesToRadians(f32, 90), 1e-6);
+    try std.testing.expectApproxEqAbs(@as(f32, -3 * pi / 2.0), degreesToRadians(f32, -270), 1e-6);
+    try std.testing.expectApproxEqAbs(@as(f32, 2 * pi), degreesToRadians(f32, 360), 1e-6);
+}
+
 /// Base-e exponential function on a floating point number.
 /// Uses a dedicated hardware instruction when available.
 /// This is the same as calling the builtin @exp