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authorven <vendethiel@hotmail.fr>2015-11-08 21:52:31 +0100
committerven <vendethiel@hotmail.fr>2015-11-08 21:52:31 +0100
commitb8ba91bd1135a94b4e0b8942417da3b0d993905a (patch)
tree22d3f37a5e98f5d44bb7ca577b1d80f2496f918e /c++.html.markdown
parent9533db901fbcf86b0509f64d95b06e3c2a1b921c (diff)
parentc3e769e4ac50d4475a530969663e073f4ff002ca (diff)
Merge pull request #1975 from zz3599/cpp-comparator
[cpp/en] comparator function for std containers
Diffstat (limited to 'c++.html.markdown')
-rw-r--r--c++.html.markdown18
1 files changed, 18 insertions, 0 deletions
diff --git a/c++.html.markdown b/c++.html.markdown
index d03092e5..6b452b1b 100644
--- a/c++.html.markdown
+++ b/c++.html.markdown
@@ -801,6 +801,24 @@ void doSomethingWithAFile(const std::string& filename)
// all automatically destroy their contents when they fall out of scope.
// - Mutexes using lock_guard and unique_lock
+// containers with object keys of non-primitive values (custom classes) require
+// compare function in the object itself or as a function pointer. Primitives
+// have default comparators, but you can override it.
+class Foo {
+public:
+ int j;
+ Foo(int a) : j(a) {}
+};
+struct compareFunction {
+ bool operator()(const Foo& a, const Foo& b) const {
+ return a.j < b.j;
+ }
+};
+//this isn't allowed (although it can vary depending on compiler)
+//std::map<Foo, int> fooMap;
+std::map<Foo, int, compareFunction> fooMap;
+fooMap[Foo(1)] = 1;
+fooMap.find(Foo(1)); //true
/////////////////////
// Fun stuff