133 lines
2.9 KiB
Zig
133 lines
2.9 KiB
Zig
// Special Cases:
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//
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// - round(+-0) = +-0
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// - round(+-inf) = +-inf
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// - round(nan) = nan
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const builtin = @import("builtin");
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const assert = @import("../debug.zig").assert;
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const math = @import("index.zig");
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pub fn round(x: var) -> @typeOf(x) {
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const T = @typeOf(x);
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switch (T) {
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f32 => @inlineCall(round32, x),
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f64 => @inlineCall(round64, x),
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else => @compileError("round not implemented for " ++ @typeName(T)),
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}
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}
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fn round32(x_: f32) -> f32 {
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var x = x_;
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const u = @bitCast(u32, x);
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const e = (u >> 23) & 0xFF;
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var y: f32 = undefined;
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if (e >= 0x7F+23) {
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return x;
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}
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if (u >> 31 != 0) {
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x = -x;
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}
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if (e < 0x7F-1) {
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math.forceEval(x + math.f32_toint);
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return 0 * @bitCast(f32, u);
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}
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{
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@setFloatMode(this, builtin.FloatMode.Strict);
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y = x + math.f32_toint - math.f32_toint - x;
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}
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if (y > 0.5) {
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y = y + x - 1;
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} else if (y <= -0.5) {
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y = y + x + 1;
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} else {
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y = y + x;
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}
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if (u >> 31 != 0) {
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-y
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} else {
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y
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}
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}
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fn round64(x_: f64) -> f64 {
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var x = x_;
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const u = @bitCast(u64, x);
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const e = (u >> 52) & 0x7FF;
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var y: f64 = undefined;
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if (e >= 0x3FF+52) {
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return x;
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}
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if (u >> 63 != 0) {
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x = -x;
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}
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if (e < 0x3ff-1) {
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math.forceEval(x + math.f64_toint);
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return 0 * @bitCast(f64, u);
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}
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{
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@setFloatMode(this, builtin.FloatMode.Strict);
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y = x + math.f64_toint - math.f64_toint - x;
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}
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if (y > 0.5) {
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y = y + x - 1;
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} else if (y <= -0.5) {
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y = y + x + 1;
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} else {
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y = y + x;
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}
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if (u >> 63 != 0) {
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-y
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} else {
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y
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}
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}
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test "math.round" {
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assert(round(f32(1.3)) == round32(1.3));
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assert(round(f64(1.3)) == round64(1.3));
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}
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test "math.round32" {
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if (builtin.os == builtin.Os.windows and builtin.arch == builtin.Arch.i386) {
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// TODO get this test passing
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// https://github.com/zig-lang/zig/issues/537
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return;
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}
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assert(round32(1.3) == 1.0);
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assert(round32(-1.3) == -1.0);
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assert(round32(0.2) == 0.0);
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assert(round32(1.8) == 2.0);
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}
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test "math.round64" {
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assert(round64(1.3) == 1.0);
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assert(round64(-1.3) == -1.0);
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assert(round64(0.2) == 0.0);
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assert(round64(1.8) == 2.0);
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}
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test "math.round32.special" {
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assert(round32(0.0) == 0.0);
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assert(round32(-0.0) == -0.0);
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assert(math.isPositiveInf(round32(math.inf(f32))));
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assert(math.isNegativeInf(round32(-math.inf(f32))));
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assert(math.isNan(round32(math.nan(f32))));
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}
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test "math.round64.special" {
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assert(round64(0.0) == 0.0);
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assert(round64(-0.0) == -0.0);
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assert(math.isPositiveInf(round64(math.inf(f64))));
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assert(math.isNegativeInf(round64(-math.inf(f64))));
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assert(math.isNan(round64(math.nan(f64))));
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}
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