[PATCH] D37417: Add range based wrapper around std::for_each.

[David Blaikie via llvm-commits]

On Mon, Sep 4, 2017 at 1:16 PM Keith Wyss <wyssman at gmail.com> wrote:

> It is an equivalent concept to range based for loop. Its not strictly
> necessary, but neither is std::for_each.
>

Right - but std::for_each existed before the range based for loop (&
admittedly, before lambdas too). I'm not sure of the motivation for this
given C++11 features/today's code.


>
> On Sep 4, 2017 9:20 AM, "David Blaikie" <dblaikie at gmail.com> wrote:
>
>> What use case do you have for this over a range-based-for loop?
>>
>> On Sat, Sep 2, 2017 at 6:08 PM Keith via Phabricator via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> kpw created this revision.
>>>
>>> There are a few range based wrappers llvm provides already. They're
>>> handy and I
>>> couldn't find one for std::for_each, so I'm adding it.
>>>
>>>
>>> https://reviews.llvm.org/D37417
>>>
>>> Files:
>>>   include/llvm/ADT/STLExtras.h
>>>   unittests/ADT/STLExtrasTest.cpp
>>>
>>>
>>> Index: unittests/ADT/STLExtrasTest.cpp
>>> ===================================================================
>>> --- unittests/ADT/STLExtrasTest.cpp
>>> +++ unittests/ADT/STLExtrasTest.cpp
>>> @@ -318,4 +318,14 @@
>>>    EXPECT_EQ(7, V[3]);
>>>  }
>>>
>>> +TEST(STLExtrasTest, ForEach) {
>>> +  std::vector<std::pair<int, int>> V = {{1, 2}, {3, 4}, {5, 6}};
>>> +  std::vector<int> Evens{};
>>> +  auto BackInserter = std::back_inserter(Evens);
>>> +  for_each(V,
>>> +           [&](std::pair<int, int> Element) { BackInserter =
>>> Element.second; });
>>> +  std::vector<int> ExpectedEvens = {2, 4, 6};
>>> +  EXPECT_EQ(Evens, ExpectedEvens);
>>> +}
>>> +
>>>  }
>>> Index: include/llvm/ADT/STLExtras.h
>>> ===================================================================
>>> --- include/llvm/ADT/STLExtras.h
>>> +++ include/llvm/ADT/STLExtras.h
>>> @@ -852,6 +852,13 @@
>>>    return std::find_if_not(std::begin(Range), std::end(Range), P);
>>>  }
>>>
>>> +/// Provide wrapper to std::for_each which take ranges instead of
>>> having to
>>> +/// pass begin/end explicitly.
>>> +template <typename R, typename UnaryFunction>
>>> +UnaryFunction for_each(R &&Range, UnaryFunction F) {
>>> +  return std::for_each(std::begin(Range), std::end(Range), F);
>>> +}
>>> +
>>>  /// Provide wrappers to std::remove_if which take ranges instead of
>>> having to
>>>  /// pass begin/end explicitly.
>>>  template <typename R, typename UnaryPredicate>
>>>
>>>
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>>
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