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Merge pull request #4107 from Feoramund/add-digit-count

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Add `core:math.count_digits_of_base`
This commit is contained in:
Jeroen van Rijn
2024-08-19 02:36:05 +02:00
committed by GitHub
parent 359a212a78 b49b80bdf9
commit 17eb0b5ee0
2 changed files with 65 additions and 1 deletions
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30
core/math/math.odin
View File

@@ -2443,6 +2443,36 @@ hypot :: proc{
hypot_f64, hypot_f64le, hypot_f64be,
}
@(require_results)
count_digits_of_base :: proc "contextless" (value: $T, $base: int) -> (digits: int) where intrinsics.type_is_integer(T) {
#assert(base >= 2, "base must be 2 or greater.")
value := value
when !intrinsics.type_is_unsigned(T) {
value = abs(value)
}
when base == 2 {
digits = max(1, 8 * size_of(T) - int(intrinsics.count_leading_zeros(value)))
} else when intrinsics.count_ones(base) == 1 {
free_bits := 8 * size_of(T) - int(intrinsics.count_leading_zeros(value))
digits, free_bits = divmod(free_bits, intrinsics.constant_log2(base))
if free_bits > 0 {
digits += 1
}
digits = max(1, digits)
} else {
digits = 1
base := cast(T)base
for value >= base {
value /= base
digits += 1
}
}
return
}
F16_DIG :: 3
F16_EPSILON :: 0.00097656
F16_GUARD :: 0

36
tests/core/math/test_core_math.odin
View File

@@ -2,6 +2,7 @@
package test_core_math
import "core:math"
import "core:strconv"
import "core:testing"
@test
@@ -1229,4 +1230,37 @@ test_large_tan :: proc(t: ^testing.T) {
f2 := math.tan(vf[i] + large)
testing.expectf(t, close(t, f1, f2), "math.tan(%.15g) = %.15g, want %.15g", vf[i]+large, f2, f1)
}
}
}
@test
test_count_digits :: proc(t: ^testing.T) {
_run_test :: proc(t: ^testing.T, $base: int) {
buf: [64]u8
for n in 0..<i64(base*base*base) {
count := math.count_digits_of_base(n, base)
str := strconv.append_int(buf[:], n, base)
if !testing.expectf(t,
len(str) == count,
"decimal %i in base-%i digit count is %i, does not match length %i of %q",
n, base, count, len(str), str) {
break
}
}
}
_run_test(t, 2)
_run_test(t, 3)
_run_test(t, 4)
_run_test(t, 5)
_run_test(t, 6)
_run_test(t, 7)
_run_test(t, 8)
_run_test(t, 9)
_run_test(t, 10)
_run_test(t, 11)
_run_test(t, 12)
_run_test(t, 13)
_run_test(t, 14)
_run_test(t, 15)
_run_test(t, 16)
}