d29871977f
We already have a LICENSE file that covers the Zig Standard Library. We no longer need to remind everyone that the license is MIT in every single file. Previously this was introduced to clarify the situation for a fork of Zig that made Zig's LICENSE file harder to find, and replaced it with their own license that required annual payments to their company. However that fork now appears to be dead. So there is no need to reinforce the copyright notice in every single file.
208 lines
5.6 KiB
Zig
208 lines
5.6 KiB
Zig
// Ported from musl, which is licensed under the MIT license:
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// https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
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//
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// https://git.musl-libc.org/cgit/musl/tree/src/math/modff.c
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// https://git.musl-libc.org/cgit/musl/tree/src/math/modf.c
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const std = @import("../std.zig");
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const math = std.math;
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const expect = std.testing.expect;
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const expectEqual = std.testing.expectEqual;
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const maxInt = std.math.maxInt;
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fn modf_result(comptime T: type) type {
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return struct {
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fpart: T,
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ipart: T,
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};
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}
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pub const modf32_result = modf_result(f32);
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pub const modf64_result = modf_result(f64);
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/// Returns the integer and fractional floating-point numbers that sum to x. The sign of each
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/// result is the same as the sign of x.
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///
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/// Special Cases:
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/// - modf(+-inf) = +-inf, nan
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/// - modf(nan) = nan, nan
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pub fn modf(x: anytype) modf_result(@TypeOf(x)) {
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const T = @TypeOf(x);
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return switch (T) {
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f32 => modf32(x),
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f64 => modf64(x),
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else => @compileError("modf not implemented for " ++ @typeName(T)),
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};
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}
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fn modf32(x: f32) modf32_result {
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var result: modf32_result = undefined;
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const u = @bitCast(u32, x);
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const e = @intCast(i32, (u >> 23) & 0xFF) - 0x7F;
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const us = u & 0x80000000;
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// TODO: Shouldn't need this.
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if (math.isInf(x)) {
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result.ipart = x;
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result.fpart = math.nan(f32);
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return result;
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}
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// no fractional part
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if (e >= 23) {
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result.ipart = x;
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if (e == 0x80 and u << 9 != 0) { // nan
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result.fpart = x;
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} else {
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result.fpart = @bitCast(f32, us);
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}
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return result;
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}
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// no integral part
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if (e < 0) {
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result.ipart = @bitCast(f32, us);
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result.fpart = x;
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return result;
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}
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const mask = @as(u32, 0x007FFFFF) >> @intCast(u5, e);
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if (u & mask == 0) {
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result.ipart = x;
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result.fpart = @bitCast(f32, us);
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return result;
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}
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const uf = @bitCast(f32, u & ~mask);
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result.ipart = uf;
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result.fpart = x - uf;
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return result;
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}
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fn modf64(x: f64) modf64_result {
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var result: modf64_result = undefined;
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const u = @bitCast(u64, x);
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const e = @intCast(i32, (u >> 52) & 0x7FF) - 0x3FF;
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const us = u & (1 << 63);
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if (math.isInf(x)) {
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result.ipart = x;
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result.fpart = math.nan(f64);
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return result;
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}
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// no fractional part
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if (e >= 52) {
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result.ipart = x;
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if (e == 0x400 and u << 12 != 0) { // nan
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result.fpart = x;
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} else {
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result.fpart = @bitCast(f64, us);
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}
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return result;
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}
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// no integral part
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if (e < 0) {
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result.ipart = @bitCast(f64, us);
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result.fpart = x;
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return result;
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}
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const mask = @as(u64, maxInt(u64) >> 12) >> @intCast(u6, e);
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if (u & mask == 0) {
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result.ipart = x;
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result.fpart = @bitCast(f64, us);
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return result;
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}
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const uf = @bitCast(f64, u & ~mask);
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result.ipart = uf;
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result.fpart = x - uf;
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return result;
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}
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test "math.modf" {
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const a = modf(@as(f32, 1.0));
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const b = modf32(1.0);
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// NOTE: No struct comparison on generic return type function? non-named, makes sense, but still.
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try expectEqual(a, b);
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}
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test "math.modf32" {
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const epsilon = 0.000001;
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var r: modf32_result = undefined;
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r = modf32(1.0);
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try expect(math.approxEqAbs(f32, r.ipart, 1.0, epsilon));
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try expect(math.approxEqAbs(f32, r.fpart, 0.0, epsilon));
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r = modf32(2.545);
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try expect(math.approxEqAbs(f32, r.ipart, 2.0, epsilon));
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try expect(math.approxEqAbs(f32, r.fpart, 0.545, epsilon));
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r = modf32(3.978123);
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try expect(math.approxEqAbs(f32, r.ipart, 3.0, epsilon));
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try expect(math.approxEqAbs(f32, r.fpart, 0.978123, epsilon));
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r = modf32(43874.3);
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try expect(math.approxEqAbs(f32, r.ipart, 43874, epsilon));
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try expect(math.approxEqAbs(f32, r.fpart, 0.300781, epsilon));
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r = modf32(1234.340780);
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try expect(math.approxEqAbs(f32, r.ipart, 1234, epsilon));
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try expect(math.approxEqAbs(f32, r.fpart, 0.340820, epsilon));
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}
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test "math.modf64" {
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const epsilon = 0.000001;
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var r: modf64_result = undefined;
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r = modf64(1.0);
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try expect(math.approxEqAbs(f64, r.ipart, 1.0, epsilon));
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try expect(math.approxEqAbs(f64, r.fpart, 0.0, epsilon));
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r = modf64(2.545);
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try expect(math.approxEqAbs(f64, r.ipart, 2.0, epsilon));
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try expect(math.approxEqAbs(f64, r.fpart, 0.545, epsilon));
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r = modf64(3.978123);
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try expect(math.approxEqAbs(f64, r.ipart, 3.0, epsilon));
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try expect(math.approxEqAbs(f64, r.fpart, 0.978123, epsilon));
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r = modf64(43874.3);
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try expect(math.approxEqAbs(f64, r.ipart, 43874, epsilon));
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try expect(math.approxEqAbs(f64, r.fpart, 0.3, epsilon));
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r = modf64(1234.340780);
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try expect(math.approxEqAbs(f64, r.ipart, 1234, epsilon));
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try expect(math.approxEqAbs(f64, r.fpart, 0.340780, epsilon));
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}
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test "math.modf32.special" {
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var r: modf32_result = undefined;
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r = modf32(math.inf(f32));
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try expect(math.isPositiveInf(r.ipart) and math.isNan(r.fpart));
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r = modf32(-math.inf(f32));
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try expect(math.isNegativeInf(r.ipart) and math.isNan(r.fpart));
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r = modf32(math.nan(f32));
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try expect(math.isNan(r.ipart) and math.isNan(r.fpart));
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}
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test "math.modf64.special" {
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var r: modf64_result = undefined;
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r = modf64(math.inf(f64));
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try expect(math.isPositiveInf(r.ipart) and math.isNan(r.fpart));
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r = modf64(-math.inf(f64));
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try expect(math.isNegativeInf(r.ipart) and math.isNan(r.fpart));
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r = modf64(math.nan(f64));
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try expect(math.isNan(r.ipart) and math.isNan(r.fpart));
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}
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