[PATCH] LWG 3040: define starts_with/ends_with as proposed
Jonathan Wakely
jwakely@redhat.com
Tue Dec 18 15:35:00 GMT 2018
* include/std/string_view [__cplusplus > 201703L]
(basic_string_view::starts_with(basic_string_view)): Implement
proposed resolution of LWG 3040 to avoid redundant length check.
(basic_string_view::starts_with(_CharT)): Implement proposed
resolution of LWG 3040 to check at most one character.
(basic_string_view::ends_with(_CharT)): Likewise.
Tested powerpc64le-linux, committed to trunk.
-------------- next part --------------
commit 6567fce9525ef70f9beaf03887213f594545c92e
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Tue Dec 18 13:53:26 2018 +0000
LWG 3040 define starts_with/ends_with as proposed
* include/std/string_view [__cplusplus > 201703L]
(basic_string_view::starts_with(basic_string_view)): Implement
proposed resolution of LWG 3040 to avoid redundant length check.
(basic_string_view::starts_with(_CharT)): Implement proposed
resolution of LWG 3040 to check at most one character.
(basic_string_view::ends_with(_CharT)): Likewise.
diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index 28d3fa46718..ac84b24314e 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -389,14 +389,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#if __cplusplus > 201703L
constexpr bool
starts_with(basic_string_view __x) const noexcept
- {
- return this->size() >= __x.size()
- && this->compare(0, __x.size(), __x) == 0;
- }
+ { return this->substr(0, __x.size()) == __x; }
constexpr bool
starts_with(_CharT __x) const noexcept
- { return this->starts_with(basic_string_view(&__x, 1)); }
+ { return !this->empty() && traits_type::eq(this->front(), __x); }
constexpr bool
starts_with(const _CharT* __x) const noexcept
@@ -411,7 +408,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr bool
ends_with(_CharT __x) const noexcept
- { return this->ends_with(basic_string_view(&__x, 1)); }
+ { return !this->empty() && traits_type::eq(this->back(), __x); }
constexpr bool
ends_with(const _CharT* __x) const noexcept
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