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// Special Cases:
//
// - floor(+-0) = +-0
// - floor(+-inf) = +-inf
// - floor(nan) = nan
const builtin = @import("builtin");
const assert = std.debug.assert;
const std = @import("../index.zig");
const math = std.math;
pub fn floor(x: var) @typeOf(x) {
const T = @typeOf(x);
return switch (T) {
f32 => floor32(x),
f64 => floor64(x),
else => @compileError("floor not implemented for " ++ @typeName(T)),
};
}
fn floor32(x: f32) f32 {
var u = @bitCast(u32, x);
const e = i32((u >> 23) & 0xFF) - 0x7F;
var m: u32 = undefined;
// TODO: Shouldn't need this explicit check.
if (x == 0.0) {
return x;
}
if (e >= 23) {
return x;
}
if (e >= 0) {
m = u32(0x007FFFFF) >> u5(e);
if (u & m == 0) {
return x;
}
math.forceEval(x + 0x1.0p120);
if (u >> 31 != 0) {
u += m;
}
return @bitCast(f32, u & ~m);
} else {
math.forceEval(x + 0x1.0p120);
if (u >> 31 == 0) {
return 0.0;
} else {
return -1.0;
}
}
}
fn floor64(x: f64) f64 {
const u = @bitCast(u64, x);
const e = (u >> 52) & 0x7FF;
var y: f64 = undefined;
if (e >= 0x3FF+52 or x == 0) {
return x;
}
if (u >> 63 != 0) {
@setFloatMode(this, builtin.FloatMode.Strict);
y = x - math.f64_toint + math.f64_toint - x;
} else {
@setFloatMode(this, builtin.FloatMode.Strict);
y = x + math.f64_toint - math.f64_toint - x;
}
if (e <= 0x3FF-1) {
math.forceEval(y);
if (u >> 63 != 0) {
return -1.0;
} else {
return 0.0;
}
} else if (y > 0) {
return x + y - 1;
} else {
return x + y;
}
}
test "math.floor" {
assert(floor(f32(1.3)) == floor32(1.3));
assert(floor(f64(1.3)) == floor64(1.3));
}
test "math.floor32" {
assert(floor32(1.3) == 1.0);
assert(floor32(-1.3) == -2.0);
assert(floor32(0.2) == 0.0);
}
test "math.floor64" {
assert(floor64(1.3) == 1.0);
assert(floor64(-1.3) == -2.0);
assert(floor64(0.2) == 0.0);
}
test "math.floor32.special" {
assert(floor32(0.0) == 0.0);
assert(floor32(-0.0) == -0.0);
assert(math.isPositiveInf(floor32(math.inf(f32))));
assert(math.isNegativeInf(floor32(-math.inf(f32))));
assert(math.isNan(floor32(math.nan(f32))));
}
test "math.floor64.special" {
assert(floor64(0.0) == 0.0);
assert(floor64(-0.0) == -0.0);
assert(math.isPositiveInf(floor64(math.inf(f64))));
assert(math.isNegativeInf(floor64(-math.inf(f64))));
assert(math.isNan(floor64(math.nan(f64))));
}
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