edponce commented on a change in pull request #10395:
URL: https://github.com/apache/arrow/pull/10395#discussion_r656530353
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File path: cpp/src/arrow/compute/kernels/scalar_arithmetic.cc
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@@ -454,6 +456,48 @@ struct PowerChecked {
}
};
+struct Sign {
+ template <typename T, typename Arg,
+ enable_if_t<std::is_floating_point<Arg>::value, bool> = true>
+ static constexpr T Call(KernelContext*, Arg arg, Status*) {
+ return (arg == 0) ? 0 : (std::signbit(arg) ? -1 : 1);
+ }
+
+ template <typename T, typename Arg,
+ enable_if_t<std::is_unsigned<Arg>::value, bool> = true>
+ static constexpr T Call(KernelContext*, Arg arg, Status*) {
+ return (arg == 0) ? 0 : 1;
+ }
+
+ template <typename T, typename Arg,
+ enable_if_t<std::is_integral<Arg>::value &&
std::is_signed<Arg>::value,
+ bool> = true>
+ static constexpr T Call(KernelContext*, Arg arg, Status*) {
+ return (arg > 0) ? 1 : ((arg == 0) ? 0 : -1);
+ }
+};
+
+struct SignWithSignedZero {
+ template <typename T, typename Arg,
+ enable_if_t<std::is_floating_point<Arg>::value, bool> = true>
+ static constexpr T Call(KernelContext*, Arg arg, Status*) {
+ return std::signbit(arg) ? -1 : 1;
+ }
+
+ template <typename T, typename Arg,
+ enable_if_t<std::is_unsigned<Arg>::value, bool> = true>
+ static constexpr T Call(KernelContext*, Arg arg, Status*) {
+ return (arg == 0) ? 0 : 1;
+ }
+
+ template <typename T, typename Arg,
+ enable_if_t<std::is_integral<Arg>::value &&
std::is_signed<Arg>::value,
+ bool> = true>
+ static constexpr T Call(KernelContext*, Arg arg, Status*) {
+ return (arg > 0) ? 1 : ((arg == 0) ? 0 : -1);
Review comment:
If zero is treated as a signed value, FP output will always be one of
(-1,1).
If zero is not signed, FP output can be (-1,0,1).
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