zig/std/math/scalbn.zig
Andrew Kelley 3671582c15 syntax: functions require return type. remove ->
The purpose of this is:

 * Only one way to do things
 * Changing a function with void return type to return a possible
   error becomes a 1 character change, subtly encouraging
   people to use errors.

See #632

Here are some imperfect sed commands for performing this update:

remove arrow:

```
sed -i 's/\(\bfn\b.*\)-> /\1/g' $(find . -name "*.zig")
```

add void:

```
sed -i 's/\(\bfn\b.*\))\s*{/\1) void {/g' $(find ../ -name "*.zig")
```

Some cleanup may be necessary, but this should do the bulk of the work.
2018-01-25 04:10:11 -05:00

86 lines
1.8 KiB
Zig

const std = @import("../index.zig");
const math = std.math;
const assert = std.debug.assert;
pub fn scalbn(x: var, n: i32) @typeOf(x) {
const T = @typeOf(x);
return switch (T) {
f32 => scalbn32(x, n),
f64 => scalbn64(x, n),
else => @compileError("scalbn not implemented for " ++ @typeName(T)),
};
}
fn scalbn32(x: f32, n_: i32) f32 {
var y = x;
var n = n_;
if (n > 127) {
y *= 0x1.0p127;
n -= 127;
if (n > 1023) {
y *= 0x1.0p127;
n -= 127;
if (n > 127) {
n = 127;
}
}
} else if (n < -126) {
y *= 0x1.0p-126 * 0x1.0p24;
n += 126 - 24;
if (n < -126) {
y *= 0x1.0p-126 * 0x1.0p24;
n += 126 - 24;
if (n < -126) {
n = -126;
}
}
}
const u = u32(n +% 0x7F) << 23;
return y * @bitCast(f32, u);
}
fn scalbn64(x: f64, n_: i32) f64 {
var y = x;
var n = n_;
if (n > 1023) {
y *= 0x1.0p1023;
n -= 1023;
if (n > 1023) {
y *= 0x1.0p1023;
n -= 1023;
if (n > 1023) {
n = 1023;
}
}
} else if (n < -1022) {
y *= 0x1.0p-1022 * 0x1.0p53;
n += 1022 - 53;
if (n < -1022) {
y *= 0x1.0p-1022 * 0x1.0p53;
n += 1022 - 53;
if (n < -1022) {
n = -1022;
}
}
}
const u = u64(n +% 0x3FF) << 52;
return y * @bitCast(f64, u);
}
test "math.scalbn" {
assert(scalbn(f32(1.5), 4) == scalbn32(1.5, 4));
assert(scalbn(f64(1.5), 4) == scalbn64(1.5, 4));
}
test "math.scalbn32" {
assert(scalbn32(1.5, 4) == 24.0);
}
test "math.scalbn64" {
assert(scalbn64(1.5, 4) == 24.0);
}