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typetraits: add toSigned, toUnsigned (#18445)

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* typetraits: add toSigned, toUnsigned

* improve and add tests

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>
Co-authored-by: flywind <xzsflywind@gmail.com>
This commit is contained in:
Timothee Cour 2022-04-07 14:38:01 -07:00 • committed by GitHub
commit e78ef57c93
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7 changed files with 85 additions and 33 deletions
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26
lib/pure/bitops.nim
View file

@ -27,7 +27,7 @@
import macros
import std/private/since
from std/private/bitops_utils import forwardImpl, toUnsigned
from std/private/bitops_utils import forwardImpl, castToUnsigned
func bitnot*[T: SomeInteger](x: T): T {.magic: "BitnotI".}
## Computes the `bitwise complement` of the integer `x`.
@ -72,7 +72,7 @@ func bitsliced*[T: SomeInteger](v: T; slice: Slice[int]): T {.inline, since: (1,
let
upmost = sizeof(T) * 8 - 1
uv = when v is SomeUnsignedInt: v else: v.toUnsigned
uv = v.castToUnsigned
(uv shl (upmost - slice.b) shr (upmost - slice.b + slice.a)).T
proc bitslice*[T: SomeInteger](v: var T; slice: Slice[int]) {.inline, since: (1, 3).} =
@ -84,7 +84,7 @@ proc bitslice*[T: SomeInteger](v: var T; slice: Slice[int]) {.inline, since: (1,
let
upmost = sizeof(T) * 8 - 1
uv = when v is SomeUnsignedInt: v else: v.toUnsigned
uv = v.castToUnsigned
v = (uv shl (upmost - slice.b) shr (upmost - slice.b + slice.a)).T
func toMask*[T: SomeInteger](slice: Slice[int]): T {.inline, since: (1, 3).} =
@ -95,10 +95,7 @@ func toMask*[T: SomeInteger](slice: Slice[int]): T {.inline, since: (1, 3).} =
let
upmost = sizeof(T) * 8 - 1
bitmask = when T is SomeUnsignedInt:
bitnot(0.T)
else:
bitnot(0.T).toUnsigned
bitmask = bitnot(0.T).castToUnsigned
(bitmask shl (upmost - slice.b + slice.a) shr (upmost - slice.b)).T
proc masked*[T: SomeInteger](v, mask :T): T {.inline, since: (1, 3).} =
@ -505,8 +502,7 @@ func parityBits*(x: SomeInteger): int {.inline.} =
# Can be used a base if creating ASM version.
# https://stackoverflow.com/questions/21617970/how-to-check-if-value-has-even-parity-of-bits-or-odd
when x is SomeSignedInt:
let x = x.toUnsigned
let x = x.castToUnsigned
when nimvm:
result = forwardImpl(parityImpl, x)
else:
@ -529,8 +525,7 @@ func firstSetBit*(x: SomeInteger): int {.inline.} =
doAssert firstSetBit(0b0000_1111'u8) == 1
# GCC builtin 'builtin_ffs' already handle zero input.
when x is SomeSignedInt:
let x = x.toUnsigned
let x = x.castToUnsigned
when nimvm:
when noUndefined:
if x == 0:
@ -572,8 +567,7 @@ func fastLog2*(x: SomeInteger): int {.inline.} =
doAssert fastLog2(0b0000_1000'u8) == 3
doAssert fastLog2(0b0000_1111'u8) == 3
when x is SomeSignedInt:
let x = x.toUnsigned
let x = x.castToUnsigned
when noUndefined:
if x == 0:
return -1
@ -615,8 +609,7 @@ func countLeadingZeroBits*(x: SomeInteger): int {.inline.} =
doAssert countLeadingZeroBits(0b0000_1000'u8) == 4
doAssert countLeadingZeroBits(0b0000_1111'u8) == 4
when x is SomeSignedInt:
let x = x.toUnsigned
let x = x.castToUnsigned
when noUndefined:
if x == 0:
return 0
@ -644,8 +637,7 @@ func countTrailingZeroBits*(x: SomeInteger): int {.inline.} =
doAssert countTrailingZeroBits(0b0000_1000'u8) == 3
doAssert countTrailingZeroBits(0b0000_1111'u8) == 0
when x is SomeSignedInt:
let x = x.toUnsigned
let x = x.castToUnsigned
when noUndefined:
if x == 0:
return 0

38
lib/pure/typetraits.nim
View file

@ -35,7 +35,7 @@ runnableExamples:
assert C[float] is HoleyEnum
proc name*(t: typedesc): string {.magic: "TypeTrait".} =
## Returns the name of the given type.
## Returns the name of `t`.
##
## Alias for `system.\`$\`(t) <dollars.html#$,typedesc>`_ since Nim v0.20.
runnableExamples:
@ -43,7 +43,7 @@ proc name*(t: typedesc): string {.magic: "TypeTrait".} =
doAssert name(seq[string]) == "seq[string]"
proc arity*(t: typedesc): int {.magic: "TypeTrait".} =
## Returns the arity of the given type. This is the number of "type"
## Returns the arity of `t`. This is the number of "type"
## components or the number of generic parameters a given type `t` has.
runnableExamples:
doAssert arity(int) == 0
@ -92,8 +92,7 @@ proc stripGenericParams*(t: typedesc): typedesc {.magic: "TypeTrait".} =
doAssert stripGenericParams(int) is int
proc supportsCopyMem*(t: typedesc): bool {.magic: "TypeTrait".}
## This trait returns true if the type `t` is safe to use for
## `copyMem`:idx:.
## Returns true if `t` is safe to use for `copyMem`:idx:.
##
## Other languages name a type like these `blob`:idx:.
@ -289,9 +288,38 @@ since (1, 1):
proc hasClosureImpl(n: NimNode): bool = discard "see compiler/vmops.nim"
proc hasClosure*(fn: NimNode): bool {.since: (1, 5, 1).} =
## Return true if the func/proc/etc `fn` has `closure`.
## Returns true if the func/proc/etc `fn` has `closure`.
## `fn` has to be a resolved symbol of kind `nnkSym`. This
## implies that the macro that calls this proc should accept `typed`
## arguments and not `untyped` arguments.
expectKind fn, nnkSym
result = hasClosureImpl(fn)
template toUnsigned*(T: typedesc[SomeInteger and not range]): untyped =
## Returns an unsigned type with same bit size as `T`.
runnableExamples:
assert int8.toUnsigned is uint8
assert uint.toUnsigned is uint
assert int.toUnsigned is uint
# range types are currently unsupported:
assert not compiles(toUnsigned(range[0..7]))
when T is int8: uint8
elif T is int16: uint16
elif T is int32: uint32
elif T is int64: uint64
elif T is int: uint
else: T
template toSigned*(T: typedesc[SomeInteger and not range]): untyped =
## Returns a signed type with same bit size as `T`.
runnableExamples:
assert int8.toSigned is int8
assert uint16.toSigned is int16
# range types are currently unsupported:
assert not compiles(toSigned(range[0..7]))
when T is uint8: int8
elif T is uint16: int16
elif T is uint32: int32
elif T is uint64: int64
elif T is uint: int
else: T