C++ 11 study notes(2/xx) simple lambda introduction

Lambda

minimum form of lambda in C++11 is like this:

#include

using namespace std;

int main() {

[](){};

return 0;

}

and it compiles. It is just a definition of minimum lambda function.

Minimum lambda function call is like this:

[](){}();

explanation of every element is below.

first "[]" is called lambda introducer. I will write usage at the end of this entry.

second () is function arguments.

third {} is function body.

last () is lambda function call.

I will introduce simple examples below.

1. hello world in lambda is like this:

[]{std::cout << "hello lambda" << std::endl;}();

it will output string "hello lambda".

2. lambda function can be assigned to variable;

auto func = []{cout << "assign to func" << endl;};

func();

3. lambda function can be passed to another function as argument.

template

void f(Func func) {

  func();

}

f([]{cout << "pass to function as argument" << endl;});

4. passing argument to lambda function

[](string const& str){cout << str << endl;}("hah");

5. declare return type of lambda function implicitly.

  auto b = []()->float { return 3.14;}();

float is return type.

6. if we want to access local names we use lambda introducer [].

string x = "I am local string which is outside of lambda function scope";

[&](string const& str){ x += str;}(". reference capture can change value of local variable");

output will be "I am local string which is outside of lambda function scope. . reference capture can change value of local variable"

copy capture is [=].

we can specify which variable is captured by reference or copy.

int x,y,z,n;

[&, x, y]{};  //only a and b is copy capture. the others are captured by reference.

[=, &x]{};   // only x is captured by reference. the others are captured by copy.

And there was tons of features.