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..0edbec4f53875267833052edde98022cd5547213 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 +133,163 @@ 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.
+// The functions here implement these for the standard containers until those
+// functions are available in the C++ standard.
+// For Chromium containers overloads should be defined 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,
+// STLEraseMemberIf - you can use them directly if the necessary
+// overload is not available or if you need non-default behavior, for example
+// erase(std::remove) for lists.
+
+// Uses erase(std::remove) idiom.
+template <typename Container, typename Value>
+void STLEraseRemove(Container& container, const Value& value) {

[danakj, 2017/03/03 20:11:49]

These should be in the base::internal namespace, but TBH I'm not clear why we're
making these helper functions. It seems like we're trying to avoid writing
erase(remove()) or erase(remove_if()) at all costs, but I don't see why we
wouldn't just call that directly as needed. It would be a lot easier to read
things if base::Erase() just did what it did, rather than calling an obscurely
named function that does the work.

[dyaroshev, 2017/03/03 23:16:54]

Done.

+  container.erase(
+      std::remove(std::begin(container), std::end(container), value),
+      std::end(container));
+}
+
+// Uses erase(std::remove) idiom.
+template <typename Container, typename Predicate>
+void STLEraseRemoveIf(Container& container, Predicate pred) {
+  container.erase(
+      std::remove_if(std::begin(container), std::end(container), pred),
+      std::end(container));
+}
+
+// Calls erase on iterators of matching elements.
+template <typename Container, typename Predicate>
+void STLEraseByOneIf(Container& container, Predicate pred) {

[danakj, 2017/03/03 20:11:49]

This maybe justifies a helper method in the internal namespace. How about
IterateAndEraseIf?

[dyaroshev, 2017/03/03 23:16:54]

Done.

+  for (auto it = std::begin(container); it != std::end(container);) {
+    if (pred(*it))
+      it = container.erase(it);
+    else
+      ++it;
+  }
+}
+
+// Calls container's remove_if method.
+template <typename Container, typename Predicate>
+void STLEraseMemberIf(Container& container, Predicate pred) {
+  container.remove_if(pred);

[danakj, 2017/03/03 20:11:49]

can't see why the caller wouldn't just call container.remove_if() here

[dyaroshev, 2017/03/03 23:16:54]

Done.

+}
+
+// Calls container's remove_if method.
+template <typename Container, typename Value>
+void STLEraseMember(Container& container, const Value& value) {
+  // Unlike std::*list::remove, this function template accepts heterogeneous
+  // 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.
+
+template <typename CharT, typename Traits, typename Allocator, typename Value>
+void STLErase(std::basic_string<CharT, Traits, Allocator>& container,

[danakj, 2017/03/03 20:11:49]

I'm not sure where the whole STL prefix thing started, but I think these should
just be base::Erase and base::EraseIf (like base::MakeUnique, for example, or
base::is_copy_assignable etc..)

[dyaroshev, 2017/03/03 23:16:54]

Done.

+              const Value& value) {
+  STLEraseRemove(container, value);
+}
+
+template <typename CharT, typename Traits, typename Allocator, class Predicate>
+void STLEraseIf(std::basic_string<CharT, Traits, Allocator>& container,
+                Predicate pred) {
+  STLEraseRemoveIf(container, pred);
+}
+
+template <class T, class Allocator, class Value>
+void STLErase(std::deque<T, Allocator>& container, const Value& value) {
+  STLEraseRemove(container, value);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::deque<T, Allocator>& container, Predicate pred) {
+  STLEraseRemoveIf(container, pred);
+}
+
+template <class T, class Allocator, class Value>
+void STLErase(std::vector<T, Allocator>& container, const Value& value) {
+  STLEraseRemove(container, value);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::vector<T, Allocator>& container, Predicate pred) {
+  STLEraseRemoveIf(container, pred);
+}
+
+template <class T, class Allocator, class Value>
+void STLErase(std::forward_list<T, Allocator>& container, const Value& value) {
+  STLEraseMember(container, value);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::forward_list<T, Allocator>& container, Predicate pred) {
+  STLEraseMemberIf(container, pred);
+}
+
+template <class T, class Allocator, class Value>
+void STLErase(std::list<T, Allocator>& container, const Value& value) {
+  STLEraseMember(container, value);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::list<T, Allocator>& container, Predicate pred) {
+  STLEraseMemberIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::map<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::multimap<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::set<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::multiset<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::unordered_map<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::unordered_multimap<T, Allocator>& container,
+                Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+template <class T, class Allocator, class Predicate>
+void STLEraseIf(std::unordered_set<T, Allocator>& container, Predicate pred) {
+  STLEraseByOneIf(container, pred);
+}
+
+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_