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authorbk2dcradle <ankitsultana@gmail.com>2016-01-05 13:36:23 +0530
committerbk2dcradle <ankitsultana@gmail.com>2016-01-05 13:36:23 +0530
commit19ead59c1fde3623bc29e1fe56f33f2587c97d3a (patch)
treefe71c415e8f63f3b29063a910945192269b67bc9 /c++.html.markdown
parent0e3ed9579b296e276741f06afe8e0a9834672b9e (diff)
Add my Changes
Diffstat (limited to 'c++.html.markdown')
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@@ -820,6 +820,73 @@ std::map<Foo, int, compareFunction> fooMap;
fooMap[Foo(1)] = 1;
fooMap.find(Foo(1)); //true
+///////////////////////////////////////
+// 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
+}
+
/////////////////////
// Fun stuff
/////////////////////