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// SPDX-License-Identifier: MIT
// Copyright (c) 2015-2020 Zig Contributors
// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
// The MIT license requires this copyright notice to be included in all copies
// and substantial portions of the software.
// Ported from go, which is licensed under a BSD-3 license.
// https://golang.org/LICENSE
//
// https://golang.org/src/math/sin.go
const builtin = @import("builtin");
const std = @import("../std.zig");
const math = std.math;
const expect = std.testing.expect;
/// Returns the sine of the radian value x.
///
/// Special Cases:
/// - sin(+-0) = +-0
/// - sin(+-inf) = nan
/// - sin(nan) = nan
pub fn sin(x: anytype) @TypeOf(x) {
const T = @TypeOf(x);
return switch (T) {
f32 => sin_(T, x),
f64 => sin_(T, x),
else => @compileError("sin not implemented for " ++ @typeName(T)),
};
}
// sin polynomial coefficients
const S0 = 1.58962301576546568060E-10;
const S1 = -2.50507477628578072866E-8;
const S2 = 2.75573136213857245213E-6;
const S3 = -1.98412698295895385996E-4;
const S4 = 8.33333333332211858878E-3;
const S5 = -1.66666666666666307295E-1;
// cos polynomial coeffiecients
const C0 = -1.13585365213876817300E-11;
const C1 = 2.08757008419747316778E-9;
const C2 = -2.75573141792967388112E-7;
const C3 = 2.48015872888517045348E-5;
const C4 = -1.38888888888730564116E-3;
const C5 = 4.16666666666665929218E-2;
const pi4a = 7.85398125648498535156e-1;
const pi4b = 3.77489470793079817668E-8;
const pi4c = 2.69515142907905952645E-15;
const m4pi = 1.273239544735162542821171882678754627704620361328125;
fn sin_(comptime T: type, x_: T) T {
const I = std.meta.Int(.signed, @typeInfo(T).Float.bits);
var x = x_;
if (x == 0 or math.isNan(x)) {
return x;
}
if (math.isInf(x)) {
return math.nan(T);
}
var sign = x < 0;
x = math.fabs(x);
var y = math.floor(x * m4pi);
var j = @floatToInt(I, y);
if (j & 1 == 1) {
j += 1;
y += 1;
}
j &= 7;
if (j > 3) {
j -= 4;
sign = !sign;
}
const z = ((x - y * pi4a) - y * pi4b) - y * pi4c;
const w = z * z;
const r = if (j == 1 or j == 2)
1.0 - 0.5 * w + w * w * (C5 + w * (C4 + w * (C3 + w * (C2 + w * (C1 + w * C0)))))
else
z + z * w * (S5 + w * (S4 + w * (S3 + w * (S2 + w * (S1 + w * S0)))));
return if (sign) -r else r;
}
test "math.sin" {
expect(sin(@as(f32, 0.0)) == sin_(f32, 0.0));
expect(sin(@as(f64, 0.0)) == sin_(f64, 0.0));
expect(comptime (math.sin(@as(f64, 2))) == math.sin(@as(f64, 2)));
}
test "math.sin32" {
const epsilon = 0.000001;
expect(math.approxEqAbs(f32, sin_(f32, 0.0), 0.0, epsilon));
expect(math.approxEqAbs(f32, sin_(f32, 0.2), 0.198669, epsilon));
expect(math.approxEqAbs(f32, sin_(f32, 0.8923), 0.778517, epsilon));
expect(math.approxEqAbs(f32, sin_(f32, 1.5), 0.997495, epsilon));
expect(math.approxEqAbs(f32, sin_(f32, -1.5), -0.997495, epsilon));
expect(math.approxEqAbs(f32, sin_(f32, 37.45), -0.246544, epsilon));
expect(math.approxEqAbs(f32, sin_(f32, 89.123), 0.916166, epsilon));
}
test "math.sin64" {
const epsilon = 0.000001;
expect(math.approxEqAbs(f64, sin_(f64, 0.0), 0.0, epsilon));
expect(math.approxEqAbs(f64, sin_(f64, 0.2), 0.198669, epsilon));
expect(math.approxEqAbs(f64, sin_(f64, 0.8923), 0.778517, epsilon));
expect(math.approxEqAbs(f64, sin_(f64, 1.5), 0.997495, epsilon));
expect(math.approxEqAbs(f64, sin_(f64, -1.5), -0.997495, epsilon));
expect(math.approxEqAbs(f64, sin_(f64, 37.45), -0.246543, epsilon));
expect(math.approxEqAbs(f64, sin_(f64, 89.123), 0.916166, epsilon));
}
test "math.sin32.special" {
expect(sin_(f32, 0.0) == 0.0);
expect(sin_(f32, -0.0) == -0.0);
expect(math.isNan(sin_(f32, math.inf(f32))));
expect(math.isNan(sin_(f32, -math.inf(f32))));
expect(math.isNan(sin_(f32, math.nan(f32))));
}
test "math.sin64.special" {
expect(sin_(f64, 0.0) == 0.0);
expect(sin_(f64, -0.0) == -0.0);
expect(math.isNan(sin_(f64, math.inf(f64))));
expect(math.isNan(sin_(f64, -math.inf(f64))));
expect(math.isNan(sin_(f64, math.nan(f64))));
}
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