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Merge pull request #830 from JordanMaples/dev/jomaples/add_missing_span_functions

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Add span::front and span::back. See #828.
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Jordan Maples [MSFT] 2020-01-10 10:20:47 -08:00 committed by GitHub
commit 888b9b9723
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2 changed files with 31 additions and 1 deletions
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16
include/gsl/span
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@ -509,13 +509,27 @@ public:
Expects(CheckRange(idx, storage_.size())); Expects(CheckRange(idx, storage_.size()));
return data()[idx]; return data()[idx];
} }
constexpr reference front() const noexcept
{
Expects(size() > 0);
return data()[0];
}
constexpr reference back() const noexcept
{
Expects(size() > 0);
return data()[size() - 1];
}
// at and operator() are deprecated to align to the public member functions of std::span // at and operator() are deprecated to align to the public member functions of std::span
[[deprecated("Use operator[]")]] [[deprecated("Use operator[]")]]
constexpr reference at(index_type idx) const noexcept{ return this->operator[](idx); } constexpr reference at(index_type idx) const noexcept{ return this->operator[](idx); }
[[deprecated("Use operator[]")]] [[deprecated("Use operator[]")]]
constexpr reference operator()(index_type idx) const noexcept{ return this->operator[](idx); } constexpr reference operator()(index_type idx) const noexcept{ return this->operator[](idx); }
constexpr pointer data() const noexcept { return storage_.data(); } constexpr pointer data() const noexcept { return storage_.data(); }
// [span.iter], span iterator support // [span.iter], span iterator support

16
tests/span_tests.cpp
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@ -1683,6 +1683,22 @@ TEST(span_test, from_array_constructor)
EXPECT_FALSE((std::is_default_constructible<span<int, 42>>::value)); EXPECT_FALSE((std::is_default_constructible<span<int, 42>>::value));
} }
TEST(span_test, front_back)
{
int arr[5] = {1,2,3,4,5};
span<int> s{arr};
EXPECT_TRUE(s.front() == 1);
EXPECT_TRUE(s.back() == 5);
std::set_terminate([] {
std::cerr << "Expected Death. front_back";
std::abort();
});
span<int> s2;
EXPECT_DEATH(s2.front(), deathstring);
EXPECT_DEATH(s2.back(), deathstring);
}
#if __clang__ || __GNUC__ #if __clang__ || __GNUC__
#pragma GCC diagnostic pop #pragma GCC diagnostic pop
#endif // __clang__ || __GNUC__ #endif // __clang__ || __GNUC__