Implementing erase/erase_if functions from library fundamentals ts:

base/stl_util.h

Index: base/stl_util.h
diff --git a/base/stl_util.h b/base/stl_util.h
index 016bb156450692415d9814f6a011446cf68ca591..6831bc60e4da3ae11fe1e0cda1012c7bc4c27504 100644
--- a/base/stl_util.h
+++ b/base/stl_util.h
@@ -8,9 +8,16 @@
 #define BASE_STL_UTIL_H_
 
 #include <algorithm>
+#include <deque>
+#include <forward_list>
 #include <functional>
 #include <iterator>
+#include <list>
+#include <map>
+#include <set>
 #include <string>
+#include <unordered_map>
+#include <unordered_set>
 #include <vector>
 
 #include "base/logging.h"
@@ -126,6 +133,195 @@ bool STLIncludes(const Arg1& a1, const Arg2& a2) {
                        a2.begin(), a2.end());
 }
 
+// STLErase/STLEraseIf are based on library fundamentals ts v2 erase/erase_if
+// http://en.cppreference.com/w/cpp/experimental/lib_extensions_2
+// They provide a generic way to erase elements from a container.
+// Here we provide overloads for standard containers and general tools to
+// implement this functions for arbitrary containers.

[dyaroshev, 2017/02/28 23:28:33]

Three times the word provide.

[Peter Kasting, 2017/03/01 03:20:10]

Nit: I would make this sentence "The functions here implement these for the
standard containers until those functions are available in the C++ standard." or
similar.

[dyaroshev, 2017/03/01 20:05:37]

Done.

+// Chromium containers should provide overloads in their own headers (like
+// standard containers).
+
+// Not container specific erasure functions -----------------------------------
+// Most of container specific functions are implemented in terms of
+// STLEraseRemove,STLEraseRemoveIf, STLEraseByOneIf, STLEraseMember,

[Peter Kasting, 2017/03/01 03:20:11]

Nit: Space after comma

[dyaroshev, 2017/03/01 20:05:37]

Done.

+// STLEraseMemberIf - you can use them directly if the necessary
+// overload is not provided here or if you need not default behavior like

[Peter Kasting, 2017/03/01 03:20:10]

Nit: not default -> non-default

[dyaroshev, 2017/03/01 20:05:37]

Done.

+// erase(std::remove) for lists.
+// Note: because there is no std::erase for associative containers, we don't
+// provide STLEraseByOne either.

[Peter Kasting, 2017/03/01 03:20:11]

Nit: I think this note is unnecessary given the similar note below on the APIs
most people actually would call.

[dyaroshev, 2017/03/01 20:05:37]

Done.

+
+// erase(std::remove) idiom.
+template <typename Container, typename Value>
+// Requires Container is a ForwardContainer,
+// Requires ValueType<Container> is Movable.
+// ValueType<Container> is equality comparable with Value.

[dyaroshev, 2017/02/28 23:28:33]

@pkasting - I know you don't like describing concepts like this but I really
hope you reconsider.
This is a modern c++ style and a version of it is suggested by c++ core
guidelines.
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#...

[Peter Kasting, 2017/03/01 03:20:11]

With respect to the folks writing the C++ Core Guidelines, who are definitely
stronger coders than me, I'm still not a fan of placing these concept-style
comments in the midst of the function declaration.  I think until the time when
they're real assertions the compiler can do something with, we'd be clearer
without them.

I think if we want to recommend doing this, it's something that should be
discussed on the cxx mailing list, not introduced one-off in individual CLs.

[dyaroshev, 2017/03/01 20:05:37]

Done.

+void STLEraseRemove(Container& container, const Value& value) {
+  container.erase(
+      std::remove(std::begin(container), std::end(container), value),
+      std::end(container));
+}
+
+// erase(std::remove) idiom.
+template <typename Container, typename Predicate>
+// Requires Container is a ForwardContainer,
+// ValueType<Container> is Movable
+// Predicate is an UnaryPredicate on ValueType<Container>.
+void STLEraseRemoveIf(Container& container, Predicate pred) {
+  container.erase(
+      std::remove_if(std::begin(container), std::end(container), pred),
+      std::end(container));
+}
+
+// erasing by one element.

[Peter Kasting, 2017/03/01 03:20:10]

Nit: Capitalize start of comment sentences (multiple places)

[dyaroshev, 2017/03/01 20:05:37]

Done.

+template <typename Container, typename Predicate>
+// Requires Predicate is an UnaryPredicate on ValueType<Container>.
+void STLEraseByOneIf(Container& container, Predicate pred) {
+  for (auto it = std::begin(container); it != std::end(container);) {
+    if (pred(*it)) {

[Peter Kasting, 2017/03/01 03:20:11]

Nit: No {}

[dyaroshev, 2017/03/01 20:05:37]

Done.

+      it = container.erase(it);
+    } else {
+      ++it;
+    }
+  }
+}
+
+// calls container's remove_if method.
+template <typename Container, typename Predicate>
+// Requires Container implements remove_if member function,
+// Predicate is an UnaryPredicate on ValueType<Container>.
+void STLEraseMemberIf(Container& container, Predicate pred) {
+  container.remove_if(pred);
+}
+
+// calls container's remove_if method.
+template <typename Container, typename Value>
+// Requires Container implements remove_if member function,
+// ValueType<Container> is equality comparable with Value.
+void STLEraseMember(Container& container, const Value& value) {
+  // Unlike std::*list::remove, this function template accepts heterogenous
+  // types and does not force a conversion to the container's value type before
+  // invoking the == operator.
+  STLEraseMemberIf(container, [&](const typename Container::value_type& cur) {
+    return cur == value;
+  });
+}
+
+// STLErase/STLEraseIf overloaded for standard containers ----------------------
+// Note: there is no std::erase for standard associative containers so we don't
+// have it either.
+
+// http://en.cppreference.com/w/cpp/experimental/basic_string/erase

[Peter Kasting, 2017/03/01 03:20:11]

Nit: I might (not sure) remove all these comments and possibly many or all of
the blank lines between the functions as well.  Basically just trying to reduce
boilerplate.

[dyaroshev, 2017/03/01 20:05:37]

I removed the comments. I don't know about the blank lines. Maybe create a
separate header and include it here?

+template <typename CharT, typename Traits, typename Allocator, typename Value>
+void STLErase(std::basic_string<CharT, Traits, Allocator>& container,
+              const Value& value) {
+  STLEraseRemove(container, value);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/basic_string/erase_if
+template <typename CharT, typename Traits, typename Allocator, class Predicate>
+void STLEraseIf(std::basic_string<CharT, Traits, Allocator>& container,
+                Predicate pred) {
+  STLEraseRemoveIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/deque/erase
+template <class T, class Allocator, class Value>
+void STLErase(std::deque<T, Allocator>& container, const Value& value) {
+  STLEraseRemove(container, value);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/deque/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::deque<T, Allocator>& container, Predicate pred) {
+  STLEraseRemoveIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/vector/erase
+template <class T, class Allocator, class Value>
+void STLErase(std::vector<T, Allocator>& container, const Value& value) {
+  STLEraseRemove(container, value);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/vector/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::vector<T, Allocator>& container, Predicate pred) {
+  STLEraseRemoveIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/forward_list/erase
+template <class T, class Allocator, class Value>
+void STLErase(std::forward_list<T, Allocator>& container, const Value& value) {
+  STLEraseMember(container, value);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/forward_list/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::forward_list<T, Allocator>& container, Predicate pred) {
+  STLEraseMemberIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/list/erase
+template <class T, class Allocator, class Value>
+void STLErase(std::list<T, Allocator>& container, const Value& value) {
+  STLEraseMember(container, value);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/list/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::list<T, Allocator>& container, Predicate pred) {
+  STLEraseMemberIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/map/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::map<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/multimap/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::multimap<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/set/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::set<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/multiset/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::multiset<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/unordered_map/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::unordered_map<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/unordered_multimap/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::unordered_multimap<T, Allocator>& container,
+                Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/unordered_set/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::unordered_set<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+// http://en.cppreference.com/w/cpp/experimental/unordered_multiset/erase_if
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::unordered_multiset<T, Allocator>& container,
+                Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
 }  // namespace base
 
 #endif  // BASE_STL_UTIL_H_