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// Special Cases:
//
// - modf(+-inf) = +-inf, nan
// - modf(nan) = nan, nan
const std = @import("../index.zig");
const math = std.math;
const assert = std.debug.assert;
fn modf_result(comptime T: type) type {
return struct {
fpart: T,
ipart: T,
};
}
pub const modf32_result = modf_result(f32);
pub const modf64_result = modf_result(f64);
pub fn modf(x: var) modf_result(@typeOf(x)) {
const T = @typeOf(x);
return switch (T) {
f32 => modf32(x),
f64 => modf64(x),
else => @compileError("modf not implemented for " ++ @typeName(T)),
};
}
fn modf32(x: f32) modf32_result {
var result: modf32_result = undefined;
const u = @bitCast(u32, x);
const e = i32((u >> 23) & 0xFF) - 0x7F;
const us = u & 0x80000000;
// TODO: Shouldn't need this.
if (math.isInf(x)) {
result.ipart = x;
result.fpart = math.nan(f32);
return result;
}
// no fractional part
if (e >= 23) {
result.ipart = x;
if (e == 0x80 and u << 9 != 0) { // nan
result.fpart = x;
} else {
result.fpart = @bitCast(f32, us);
}
return result;
}
// no integral part
if (e < 0) {
result.ipart = @bitCast(f32, us);
result.fpart = x;
return result;
}
const mask = u32(0x007FFFFF) >> u5(e);
if (u & mask == 0) {
result.ipart = x;
result.fpart = @bitCast(f32, us);
return result;
}
const uf = @bitCast(f32, u & ~mask);
result.ipart = uf;
result.fpart = x - uf;
return result;
}
fn modf64(x: f64) modf64_result {
var result: modf64_result = undefined;
const u = @bitCast(u64, x);
const e = i32((u >> 52) & 0x7FF) - 0x3FF;
const us = u & (1 << 63);
if (math.isInf(x)) {
result.ipart = x;
result.fpart = math.nan(f64);
return result;
}
// no fractional part
if (e >= 52) {
result.ipart = x;
if (e == 0x400 and u << 12 != 0) { // nan
result.fpart = x;
} else {
result.fpart = @bitCast(f64, us);
}
return result;
}
// no integral part
if (e < 0) {
result.ipart = @bitCast(f64, us);
result.fpart = x;
return result;
}
const mask = u64(@maxValue(u64) >> 12) >> u6(e);
if (u & mask == 0) {
result.ipart = x;
result.fpart = @bitCast(f64, us);
return result;
}
const uf = @bitCast(f64, u & ~mask);
result.ipart = uf;
result.fpart = x - uf;
return result;
}
test "math.modf" {
const a = modf(f32(1.0));
const b = modf32(1.0);
// NOTE: No struct comparison on generic return type function? non-named, makes sense, but still.
assert(a.ipart == b.ipart and a.fpart == b.fpart);
const c = modf(f64(1.0));
const d = modf64(1.0);
assert(a.ipart == b.ipart and a.fpart == b.fpart);
}
test "math.modf32" {
const epsilon = 0.000001;
var r: modf32_result = undefined;
r = modf32(1.0);
assert(math.approxEq(f32, r.ipart, 1.0, epsilon));
assert(math.approxEq(f32, r.fpart, 0.0, epsilon));
r = modf32(2.545);
assert(math.approxEq(f32, r.ipart, 2.0, epsilon));
assert(math.approxEq(f32, r.fpart, 0.545, epsilon));
r = modf32(3.978123);
assert(math.approxEq(f32, r.ipart, 3.0, epsilon));
assert(math.approxEq(f32, r.fpart, 0.978123, epsilon));
r = modf32(43874.3);
assert(math.approxEq(f32, r.ipart, 43874, epsilon));
assert(math.approxEq(f32, r.fpart, 0.300781, epsilon));
r = modf32(1234.340780);
assert(math.approxEq(f32, r.ipart, 1234, epsilon));
assert(math.approxEq(f32, r.fpart, 0.340820, epsilon));
}
test "math.modf64" {
const epsilon = 0.000001;
var r: modf64_result = undefined;
r = modf64(1.0);
assert(math.approxEq(f64, r.ipart, 1.0, epsilon));
assert(math.approxEq(f64, r.fpart, 0.0, epsilon));
r = modf64(2.545);
assert(math.approxEq(f64, r.ipart, 2.0, epsilon));
assert(math.approxEq(f64, r.fpart, 0.545, epsilon));
r = modf64(3.978123);
assert(math.approxEq(f64, r.ipart, 3.0, epsilon));
assert(math.approxEq(f64, r.fpart, 0.978123, epsilon));
r = modf64(43874.3);
assert(math.approxEq(f64, r.ipart, 43874, epsilon));
assert(math.approxEq(f64, r.fpart, 0.3, epsilon));
r = modf64(1234.340780);
assert(math.approxEq(f64, r.ipart, 1234, epsilon));
assert(math.approxEq(f64, r.fpart, 0.340780, epsilon));
}
test "math.modf32.special" {
var r: modf32_result = undefined;
r = modf32(math.inf(f32));
assert(math.isPositiveInf(r.ipart) and math.isNan(r.fpart));
r = modf32(-math.inf(f32));
assert(math.isNegativeInf(r.ipart) and math.isNan(r.fpart));
r = modf32(math.nan(f32));
assert(math.isNan(r.ipart) and math.isNan(r.fpart));
}
test "math.modf64.special" {
var r: modf64_result = undefined;
r = modf64(math.inf(f64));
assert(math.isPositiveInf(r.ipart) and math.isNan(r.fpart));
r = modf64(-math.inf(f64));
assert(math.isNegativeInf(r.ipart) and math.isNan(r.fpart));
r = modf64(math.nan(f64));
assert(math.isNan(r.ipart) and math.isNan(r.fpart));
}
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