4c16f9a3c3
This covers the majority of the functions as covered by the C99 specification for a math library. Code is adapted primarily from musl libc, with the pow and standard trigonometric functions adapted from the Go stdlib. Changes: - Remove assert expose in index and import as needed. - Add float log function and merge with existing base 2 integer implementation. See https://github.com/tiehuis/zig-fmath. See #374.
73 lines
2.2 KiB
Zig
73 lines
2.2 KiB
Zig
const math = @import("index.zig");
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const builtin = @import("builtin");
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const assert = @import("../debug.zig").assert;
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pub fn log(comptime base: usize, x: var) -> @typeOf(x) {
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const T = @typeOf(x);
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switch (@typeId(T)) {
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builtin.TypeId.Int => {
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if (base == 2) {
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return T.bit_count - 1 - @clz(x);
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} else {
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@compileError("TODO implement log for non base 2 integers");
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}
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},
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builtin.TypeId.Float => {
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return logf(base, x);
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},
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else => {
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@compileError("log expects integer or float, found '" ++ @typeName(T) ++ "'");
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},
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}
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}
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fn logf(comptime base: usize, x: var) -> @typeOf(x) {
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const T = @typeOf(x);
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switch (T) {
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f32 => {
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switch (base) {
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2 => return math.log2(x),
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10 => return math.log10(x),
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else => return f32(math.ln(f64(x)) / math.ln(f64(base))),
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}
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},
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f64 => {
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switch (base) {
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2 => return math.log2(x),
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10 => return math.log10(x),
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// NOTE: This likely is computed with reduced accuracy.
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else => return math.ln(x) / math.ln(f64(base)),
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}
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},
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else => @compileError("log not implemented for " ++ @typeName(T)),
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}
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}
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test "log_integer" {
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assert(log(2, u8(0x1)) == 0);
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assert(log(2, u8(0x2)) == 1);
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assert(log(2, i16(0x72)) == 6);
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assert(log(2, u32(0xFFFFFF)) == 23);
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assert(log(2, u64(0x7FF0123456789ABC)) == 62);
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}
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test "log_float" {
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const epsilon = 0.000001;
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assert(math.approxEq(f32, log(6, f32(0.23947)), -0.797723, epsilon));
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assert(math.approxEq(f32, log(89, f32(0.23947)), -0.318432, epsilon));
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assert(math.approxEq(f64, log(123897, f64(12389216414)), 1.981724596, epsilon));
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}
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test "log_float_special" {
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assert(log(2, f32(0.2301974)) == math.log2(f32(0.2301974)));
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assert(log(10, f32(0.2301974)) == math.log10(f32(0.2301974)));
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assert(log(2, f64(213.23019799993)) == math.log2(f64(213.23019799993)));
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assert(log(10, f64(213.23019799993)) == math.log10(f64(213.23019799993)));
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}
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