On 29/11/18 21:35 -0500, Ed Smith-Rowland wrote:
Greetings,
This patch implements starts_with and ends_with for basic_string and
basic_string_view for C++20.
This was on my TODO list, thanks for taking care of it.
+#if __cplusplus > 201703L
+ bool
+ starts_with(basic_string_view<_CharT, _Traits> __x) const noexcept
+ { return __sv_type(this->data(), this->size()).starts_with(__x); }
+
+ bool
+ starts_with(_CharT __x) const noexcept
+ { return __sv_type(this->data(), this->size()).starts_with(__x); }
+
+ bool
+ starts_with(const _CharT* __x) const
This can be noexcept. It isn't in the standard, because it has a
narrow contract (there's a precondition that __x is null-terminated).
But since we can't reliably detect whether __x is null-terminated, and
even if we could we wouldn't want to throw an exception, we can just
make it noexcept. Same for the ends_with(const _CharT*) one, and the
equivalent members in the COW basic_string and basic_string_view.
Index: include/std/string_view
===================================================================
--- include/std/string_view (revision 266645)
+++ include/std/string_view (working copy)
@@ -227,7 +227,6 @@
__sv = __tmp;
}
-
// [string.view.ops], string operations:
size_type
@@ -387,6 +386,36 @@
traits_type::length(__str));
}
+#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; }
Please put the opening and closing braces on their own lines, as for
ends_with below:
+ constexpr bool
+ ends_with(basic_string_view __x) const noexcept
+ {
+ return this->size() >= __x.size()
+ && this->compare(this->size() - __x.size(), npos, __x) == 0;
+ }
OK with those changes, thanks.
