pub fn expect(ok: bool) !voidThis function is intended to be used only in tests. When ok is false, returns a test failure error.
pub fn maxInt(comptime T: type) comptime_intReturns the maximum value of integer type T.
pub fn minInt(comptime T: type) comptime_intReturns the minimum value of integer type T.
pub fn ilogb(x: anytype) i32Returns the binary exponent of x as an integer.
Special Cases:
fn ilogbX(comptime T: type, x: T) i321
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172// Ported from musl, which is MIT licensed.
// https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
//
// https://git.musl-libc.org/cgit/musl/tree/src/math/ilogbl.c
// https://git.musl-libc.org/cgit/musl/tree/src/math/ilogbf.c
// https://git.musl-libc.org/cgit/musl/tree/src/math/ilogb.c
const std = @import("../std.zig");
const math = std.math;
const expect = std.testing.expect;
const maxInt = std.math.maxInt;
const minInt = std.math.minInt;
/// Returns the binary exponent of x as an integer.
///
/// Special Cases:
/// - ilogb(+-inf) = maxInt(i32)
/// - ilogb(+-0) = minInt(i32)
/// - ilogb(nan) = minInt(i32)
pub fn ilogb(x: anytype) i32 {
const T = @TypeOf(x);
return ilogbX(T, x);
}
pub const fp_ilogbnan = minInt(i32);
pub const fp_ilogb0 = minInt(i32);
fn ilogbX(comptime T: type, x: T) i32 {
const typeWidth = @typeInfo(T).float.bits;
const significandBits = math.floatMantissaBits(T);
const exponentBits = math.floatExponentBits(T);
const Z = @Int(.unsigned, typeWidth);
const signBit = (@as(Z, 1) << (significandBits + exponentBits));
const maxExponent = ((1 << exponentBits) - 1);
const exponentBias = (maxExponent >> 1);
const absMask = signBit - 1;
const u = @as(Z, @bitCast(x)) & absMask;
const e: i32 = @intCast(u >> significandBits);
if (e == 0) {
if (u == 0) {
math.raiseInvalid();
return fp_ilogb0;
}
// offset sign bit, exponent bits, and integer bit (if present) + bias
const offset = 1 + exponentBits + @as(comptime_int, @intFromBool(T == f80)) - exponentBias;
return offset - @as(i32, @intCast(@clz(u)));
}
if (e == maxExponent) {
math.raiseInvalid();
if (u > @as(Z, @bitCast(math.inf(T)))) {
return fp_ilogbnan; // u is a NaN
} else return maxInt(i32);
}
return e - exponentBias;
}
test "type dispatch" {
try expect(ilogb(@as(f32, 0.2)) == ilogbX(f32, 0.2));
try expect(ilogb(@as(f64, 0.2)) == ilogbX(f64, 0.2));
}
test "16" {
try expect(ilogbX(f16, 0.0) == fp_ilogb0);
try expect(ilogbX(f16, 0.5) == -1);
try expect(ilogbX(f16, 0.8923) == -1);
try expect(ilogbX(f16, 10.0) == 3);
try expect(ilogbX(f16, -65504) == 15);
try expect(ilogbX(f16, 2398.23) == 11);
try expect(ilogbX(f16, 0x1p-1) == -1);
try expect(ilogbX(f16, 0x1p-17) == -17);
try expect(ilogbX(f16, 0x1p-24) == -24);
}
test "32" {
try expect(ilogbX(f32, 0.0) == fp_ilogb0);
try expect(ilogbX(f32, 0.5) == -1);
try expect(ilogbX(f32, 0.8923) == -1);
try expect(ilogbX(f32, 10.0) == 3);
try expect(ilogbX(f32, -123984) == 16);
try expect(ilogbX(f32, 2398.23) == 11);
try expect(ilogbX(f32, 0x1p-1) == -1);
try expect(ilogbX(f32, 0x1p-122) == -122);
try expect(ilogbX(f32, 0x1p-127) == -127);
}
test "64" {
try expect(ilogbX(f64, 0.0) == fp_ilogb0);
try expect(ilogbX(f64, 0.5) == -1);
try expect(ilogbX(f64, 0.8923) == -1);
try expect(ilogbX(f64, 10.0) == 3);
try expect(ilogbX(f64, -123984) == 16);
try expect(ilogbX(f64, 2398.23) == 11);
try expect(ilogbX(f64, 0x1p-1) == -1);
try expect(ilogbX(f64, 0x1p-127) == -127);
try expect(ilogbX(f64, 0x1p-1012) == -1012);
try expect(ilogbX(f64, 0x1p-1023) == -1023);
}
test "80" {
try expect(ilogbX(f80, 0.0) == fp_ilogb0);
try expect(ilogbX(f80, 0.5) == -1);
try expect(ilogbX(f80, 0.8923) == -1);
try expect(ilogbX(f80, 10.0) == 3);
try expect(ilogbX(f80, -123984) == 16);
try expect(ilogbX(f80, 2398.23) == 11);
try expect(ilogbX(f80, 0x1p-1) == -1);
try expect(ilogbX(f80, 0x1p-127) == -127);
try expect(ilogbX(f80, 0x1p-1023) == -1023);
try expect(ilogbX(f80, 0x1p-16383) == -16383);
}
test "128" {
try expect(ilogbX(f128, 0.0) == fp_ilogb0);
try expect(ilogbX(f128, 0.5) == -1);
try expect(ilogbX(f128, 0.8923) == -1);
try expect(ilogbX(f128, 10.0) == 3);
try expect(ilogbX(f128, -123984) == 16);
try expect(ilogbX(f128, 2398.23) == 11);
try expect(ilogbX(f128, 0x1p-1) == -1);
try expect(ilogbX(f128, 0x1p-127) == -127);
try expect(ilogbX(f128, 0x1p-1023) == -1023);
try expect(ilogbX(f128, 0x1p-16383) == -16383);
}
test "16 special" {
try expect(ilogbX(f16, math.inf(f16)) == maxInt(i32));
try expect(ilogbX(f16, -math.inf(f16)) == maxInt(i32));
try expect(ilogbX(f16, 0.0) == minInt(i32));
try expect(ilogbX(f16, math.nan(f16)) == fp_ilogbnan);
}
test "32 special" {
try expect(ilogbX(f32, math.inf(f32)) == maxInt(i32));
try expect(ilogbX(f32, -math.inf(f32)) == maxInt(i32));
try expect(ilogbX(f32, 0.0) == minInt(i32));
try expect(ilogbX(f32, math.nan(f32)) == fp_ilogbnan);
}
test "64 special" {
try expect(ilogbX(f64, math.inf(f64)) == maxInt(i32));
try expect(ilogbX(f64, -math.inf(f64)) == maxInt(i32));
try expect(ilogbX(f64, 0.0) == minInt(i32));
try expect(ilogbX(f64, math.nan(f64)) == fp_ilogbnan);
}
test "80 special" {
try expect(ilogbX(f80, math.inf(f80)) == maxInt(i32));
try expect(ilogbX(f80, -math.inf(f80)) == maxInt(i32));
try expect(ilogbX(f80, 0.0) == minInt(i32));
try expect(ilogbX(f80, math.nan(f80)) == fp_ilogbnan);
}
test "128 special" {
try expect(ilogbX(f128, math.inf(f128)) == maxInt(i32));
try expect(ilogbX(f128, -math.inf(f128)) == maxInt(i32));
try expect(ilogbX(f128, 0.0) == minInt(i32));
try expect(ilogbX(f128, math.nan(f128)) == fp_ilogbnan);
}