1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
|
// Ported from musl, which is licensed under the MIT license:
// https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
//
// https://git.musl-libc.org/cgit/musl/tree/src/math/modff.c
// https://git.musl-libc.org/cgit/musl/tree/src/math/modf.c
const std = @import("../std.zig");
const math = std.math;
const expect = std.testing.expect;
const expectEqual = std.testing.expectEqual;
const maxInt = std.math.maxInt;
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);
/// Returns the integer and fractional floating-point numbers that sum to x. The sign of each
/// result is the same as the sign of x.
///
/// Special Cases:
/// - modf(+-inf) = +-inf, nan
/// - modf(nan) = nan, nan
pub fn modf(x: anytype) 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 = @intCast(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 = @as(u32, 0x007FFFFF) >> @intCast(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 = @intCast(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 = @as(u64, maxInt(u64) >> 12) >> @intCast(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(@as(f32, 1.0));
const b = modf32(1.0);
// NOTE: No struct comparison on generic return type function? non-named, makes sense, but still.
try expectEqual(a, b);
}
test "math.modf32" {
const epsilon = 0.000001;
var r: modf32_result = undefined;
r = modf32(1.0);
try expect(math.approxEqAbs(f32, r.ipart, 1.0, epsilon));
try expect(math.approxEqAbs(f32, r.fpart, 0.0, epsilon));
r = modf32(2.545);
try expect(math.approxEqAbs(f32, r.ipart, 2.0, epsilon));
try expect(math.approxEqAbs(f32, r.fpart, 0.545, epsilon));
r = modf32(3.978123);
try expect(math.approxEqAbs(f32, r.ipart, 3.0, epsilon));
try expect(math.approxEqAbs(f32, r.fpart, 0.978123, epsilon));
r = modf32(43874.3);
try expect(math.approxEqAbs(f32, r.ipart, 43874, epsilon));
try expect(math.approxEqAbs(f32, r.fpart, 0.300781, epsilon));
r = modf32(1234.340780);
try expect(math.approxEqAbs(f32, r.ipart, 1234, epsilon));
try expect(math.approxEqAbs(f32, r.fpart, 0.340820, epsilon));
}
test "math.modf64" {
const epsilon = 0.000001;
var r: modf64_result = undefined;
r = modf64(1.0);
try expect(math.approxEqAbs(f64, r.ipart, 1.0, epsilon));
try expect(math.approxEqAbs(f64, r.fpart, 0.0, epsilon));
r = modf64(2.545);
try expect(math.approxEqAbs(f64, r.ipart, 2.0, epsilon));
try expect(math.approxEqAbs(f64, r.fpart, 0.545, epsilon));
r = modf64(3.978123);
try expect(math.approxEqAbs(f64, r.ipart, 3.0, epsilon));
try expect(math.approxEqAbs(f64, r.fpart, 0.978123, epsilon));
r = modf64(43874.3);
try expect(math.approxEqAbs(f64, r.ipart, 43874, epsilon));
try expect(math.approxEqAbs(f64, r.fpart, 0.3, epsilon));
r = modf64(1234.340780);
try expect(math.approxEqAbs(f64, r.ipart, 1234, epsilon));
try expect(math.approxEqAbs(f64, r.fpart, 0.340780, epsilon));
}
test "math.modf32.special" {
var r: modf32_result = undefined;
r = modf32(math.inf(f32));
try expect(math.isPositiveInf(r.ipart) and math.isNan(r.fpart));
r = modf32(-math.inf(f32));
try expect(math.isNegativeInf(r.ipart) and math.isNan(r.fpart));
r = modf32(math.nan(f32));
try expect(math.isNan(r.ipart) and math.isNan(r.fpart));
}
test "math.modf64.special" {
var r: modf64_result = undefined;
r = modf64(math.inf(f64));
try expect(math.isPositiveInf(r.ipart) and math.isNan(r.fpart));
r = modf64(-math.inf(f64));
try expect(math.isNegativeInf(r.ipart) and math.isNan(r.fpart));
r = modf64(math.nan(f64));
try expect(math.isNan(r.ipart) and math.isNan(r.fpart));
}
|
