diff options
author | bk2dcradle <ankitsultana@gmail.com> | 2016-01-05 13:34:10 +0530 |
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committer | bk2dcradle <ankitsultana@gmail.com> | 2016-01-05 13:34:10 +0530 |
commit | 0e3ed9579b296e276741f06afe8e0a9834672b9e (patch) | |
tree | d01a82820ee8a7fb41583cdbf9119583d3fe8004 /c++.html.markdown | |
parent | a5730e4ab931b8355704d35ee08acef75435bd83 (diff) | |
parent | 4dc5eeda5528047ece4f5798cff6961b0bc21dcb (diff) |
Reset to Adambard's
Diffstat (limited to 'c++.html.markdown')
-rw-r--r-- | c++.html.markdown | 86 |
1 files changed, 19 insertions, 67 deletions
diff --git a/c++.html.markdown b/c++.html.markdown index c1bacf6a..f4aa2f5a 100644 --- a/c++.html.markdown +++ b/c++.html.markdown @@ -149,7 +149,7 @@ namespace First { namespace Second { void foo() { - printf("This is Second::foo\n") + printf("This is Second::foo\n"); } } @@ -801,72 +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 -/////////////////////////////////////// -// Lambda Expressions (C++11 and above) -/////////////////////////////////////// - -// lambdas are a convenient way of defining an anonymous function -// object right at the location where it is invoked or passed as -// an argument to a function. - -// For example, consider sorting a vector of pairs using the second -// value of the pair - -vector<pair<int, int> > tester; -tester.push_back(make_pair(3, 6)); -tester.push_back(make_pair(1, 9)); -tester.push_back(make_pair(5, 0)); - -// Pass a lambda expression as third argument to the sort function -// sort is from the <algorithm> header - -sort(tester.begin(), tester.end(), [](const pair<int, int>& lhs, const pair<int, int>& rhs) { - return lhs.second < rhs.second; - }); - -// Notice the syntax of the lambda expression, -// [] in the lambda is used to "capture" variables. -// For Example: - -vector<int> dog_ids; -// number_of_dogs = 3; -for(int i = 0; i < 3; i++){ - dog_ids.push_back(i); -} - -int weight[3] = {30, 50, 10}; - -// Say you want to sort dog_ids according to the dogs' weights -// So dog_ids should in the end become: [2, 0, 1] - -// Here's where lambda expressions come in handy - -sort(dog_ids.begin(), dog_ids.end(), [&weight](const int &lhs, const int &rhs) { - return weight[lhs] < weight[rhs]; - }); -// Note we captured "weight" by reference in the above example. - -// lambda are really useful for the case of structs -// You can use lambda expressions instead of overloading -// the "<" operator - -/////////////////////////////// -// Range For (C++11 and above) -/////////////////////////////// - -// You can use a range for loop to iterate over a container -int arr[] = {1, 10, 3}; - -for(int elem: arr){ - cout << elem << endl; -} - -// You can use "auto" and not worry about the type of the elements of the container -// For example: - -for(auto elem: arr) { - // Do something with each element of arr -} +// 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 |