[v3] is_modulo
Marc Glisse
marc.glisse@inria.fr
Sat Apr 28 22:42:00 GMT 2012
Hello,
the attached follows the precisions on the definition of is_modulo in
DR 612. I believe this is what the values always should have been, so I
didn't make the change conditional to C++11.
PR 22200 can remain open if people want to discuss the interaction with
-fwrapv, but false is the safe value.
I ran the testsuite, to make sure there wasn't a huge typo that would
prevent the file from compiling, and the only failure was the usual
22_locale/time_get/get_date/wchar_t/4.cc.
2012-04-29 Marc Glisse <marc.glisse@inria.fr>
PR libstdc++/22200
* include/std/limits (numeric_limits<>::is_modulo): false for
signed types.
--
Marc Glisse
-------------- next part --------------
Index: include/std/limits
===================================================================
--- include/std/limits (revision 186932)
+++ include/std/limits (working copy)
@@ -268,14 +268,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
/** <em>True if the set of values representable by the type is
finite. All built-in types are bounded, this member would be
false for arbitrary precision types.</em> [18.2.1.2]/54 */
static _GLIBCXX_USE_CONSTEXPR bool is_bounded = false;
- /** True if the type is @e modulo, that is, if it is possible to add two
- positive numbers and have a result that wraps around to a third number
- that is less. Typically false for floating types, true for unsigned
- integers, and true for signed integers. */
+ /** True if the type is @e modulo. A type is modulo if, for any
+ operation involving +, -, or * on values of that type whose
+ result would fall outside the range [min(),max()], the value
+ returned differs from the true value by an integer multiple of
+ max() - min() + 1. On most machines, this is false for floating
+ types, true for unsigned integers, and true for signed integers.
+ See PR22200 about signed integers. */
static _GLIBCXX_USE_CONSTEXPR bool is_modulo = false;
/** True if trapping is implemented for this type. */
static _GLIBCXX_USE_CONSTEXPR bool traps = false;
@@ -492,11 +495,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _GLIBCXX_CONSTEXPR char
denorm_min() _GLIBCXX_USE_NOEXCEPT { return static_cast<char>(0); }
static _GLIBCXX_USE_CONSTEXPR bool is_iec559 = false;
static _GLIBCXX_USE_CONSTEXPR bool is_bounded = true;
- static _GLIBCXX_USE_CONSTEXPR bool is_modulo = true;
+ static _GLIBCXX_USE_CONSTEXPR bool is_modulo = !is_signed;
static _GLIBCXX_USE_CONSTEXPR bool traps = __glibcxx_integral_traps;
static _GLIBCXX_USE_CONSTEXPR bool tinyness_before = false;
static _GLIBCXX_USE_CONSTEXPR float_round_style round_style
= round_toward_zero;
@@ -562,11 +565,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
denorm_min() _GLIBCXX_USE_NOEXCEPT
{ return static_cast<signed char>(0); }
static _GLIBCXX_USE_CONSTEXPR bool is_iec559 = false;
static _GLIBCXX_USE_CONSTEXPR bool is_bounded = true;
- static _GLIBCXX_USE_CONSTEXPR bool is_modulo = true;
+ static _GLIBCXX_USE_CONSTEXPR bool is_modulo = false;
static _GLIBCXX_USE_CONSTEXPR bool traps = __glibcxx_integral_traps;
static _GLIBCXX_USE_CONSTEXPR bool tinyness_before = false;
static _GLIBCXX_USE_CONSTEXPR float_round_style round_style
= round_toward_zero;
@@ -703,11 +706,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _GLIBCXX_CONSTEXPR wchar_t
denorm_min() _GLIBCXX_USE_NOEXCEPT { return wchar_t(); }
static _GLIBCXX_USE_CONSTEXPR bool is_iec559 = false;
static _GLIBCXX_USE_CONSTEXPR bool is_bounded = true;
- static _GLIBCXX_USE_CONSTEXPR bool is_modulo = true;
+ static _GLIBCXX_USE_CONSTEXPR bool is_modulo = !is_signed;
static _GLIBCXX_USE_CONSTEXPR bool traps = __glibcxx_integral_traps;
static _GLIBCXX_USE_CONSTEXPR bool tinyness_before = false;
static _GLIBCXX_USE_CONSTEXPR float_round_style round_style
= round_toward_zero;
@@ -766,11 +769,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static constexpr char16_t
denorm_min() noexcept { return char16_t(); }
static constexpr bool is_iec559 = false;
static constexpr bool is_bounded = true;
- static constexpr bool is_modulo = true;
+ static constexpr bool is_modulo = !is_signed;
static constexpr bool traps = __glibcxx_integral_traps;
static constexpr bool tinyness_before = false;
static constexpr float_round_style round_style = round_toward_zero;
};
@@ -827,11 +830,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static constexpr char32_t
denorm_min() noexcept { return char32_t(); }
static constexpr bool is_iec559 = false;
static constexpr bool is_bounded = true;
- static constexpr bool is_modulo = true;
+ static constexpr bool is_modulo = !is_signed;
static constexpr bool traps = __glibcxx_integral_traps;
static constexpr bool tinyness_before = false;
static constexpr float_round_style round_style = round_toward_zero;
};
@@ -894,11 +897,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _GLIBCXX_CONSTEXPR short
denorm_min() _GLIBCXX_USE_NOEXCEPT { return short(); }
static _GLIBCXX_USE_CONSTEXPR bool is_iec559 = false;
static _GLIBCXX_USE_CONSTEXPR bool is_bounded = true;
- static _GLIBCXX_USE_CONSTEXPR bool is_modulo = true;
+ static _GLIBCXX_USE_CONSTEXPR bool is_modulo = false;
static _GLIBCXX_USE_CONSTEXPR bool traps = __glibcxx_integral_traps;
static _GLIBCXX_USE_CONSTEXPR bool tinyness_before = false;
static _GLIBCXX_USE_CONSTEXPR float_round_style round_style
= round_toward_zero;
@@ -1034,11 +1037,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _GLIBCXX_CONSTEXPR int
denorm_min() _GLIBCXX_USE_NOEXCEPT { return static_cast<int>(0); }
static _GLIBCXX_USE_CONSTEXPR bool is_iec559 = false;
static _GLIBCXX_USE_CONSTEXPR bool is_bounded = true;
- static _GLIBCXX_USE_CONSTEXPR bool is_modulo = true;
+ static _GLIBCXX_USE_CONSTEXPR bool is_modulo = false;
static _GLIBCXX_USE_CONSTEXPR bool traps = __glibcxx_integral_traps;
static _GLIBCXX_USE_CONSTEXPR bool tinyness_before = false;
static _GLIBCXX_USE_CONSTEXPR float_round_style round_style
= round_toward_zero;
@@ -1173,11 +1176,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _GLIBCXX_CONSTEXPR long
denorm_min() _GLIBCXX_USE_NOEXCEPT { return static_cast<long>(0); }
static _GLIBCXX_USE_CONSTEXPR bool is_iec559 = false;
static _GLIBCXX_USE_CONSTEXPR bool is_bounded = true;
- static _GLIBCXX_USE_CONSTEXPR bool is_modulo = true;
+ static _GLIBCXX_USE_CONSTEXPR bool is_modulo = false;
static _GLIBCXX_USE_CONSTEXPR bool traps = __glibcxx_integral_traps;
static _GLIBCXX_USE_CONSTEXPR bool tinyness_before = false;
static _GLIBCXX_USE_CONSTEXPR float_round_style round_style
= round_toward_zero;
@@ -1316,11 +1319,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _GLIBCXX_CONSTEXPR long long
denorm_min() _GLIBCXX_USE_NOEXCEPT { return static_cast<long long>(0); }
static _GLIBCXX_USE_CONSTEXPR bool is_iec559 = false;
static _GLIBCXX_USE_CONSTEXPR bool is_bounded = true;
- static _GLIBCXX_USE_CONSTEXPR bool is_modulo = true;
+ static _GLIBCXX_USE_CONSTEXPR bool is_modulo = false;
static _GLIBCXX_USE_CONSTEXPR bool traps = __glibcxx_integral_traps;
static _GLIBCXX_USE_CONSTEXPR bool tinyness_before = false;
static _GLIBCXX_USE_CONSTEXPR float_round_style round_style
= round_toward_zero;
@@ -1463,11 +1466,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
denorm_min() _GLIBCXX_USE_NOEXCEPT
{ return static_cast<__int128>(0); }
static _GLIBCXX_USE_CONSTEXPR bool is_iec559 = false;
static _GLIBCXX_USE_CONSTEXPR bool is_bounded = true;
- static _GLIBCXX_USE_CONSTEXPR bool is_modulo = true;
+ static _GLIBCXX_USE_CONSTEXPR bool is_modulo = false;
static _GLIBCXX_USE_CONSTEXPR bool traps
= __glibcxx_integral_traps;
static _GLIBCXX_USE_CONSTEXPR bool tinyness_before = false;
static _GLIBCXX_USE_CONSTEXPR float_round_style round_style
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