Lambda Functions

Lambda functions, or anonymous functions, are a feature that allows you to create small, unnamed functions inline in your code. They are particularly useful when you need a simple function for a short period of time and don't want to define a separate named function.

Lambda functions are useful for several reasons:

Conciseness: Lambda functions allow you to write short and concise code. They are ideal for operations that can be expressed in a few lines.
Local Scope: They can capture variables from the surrounding scope, allowing you to use variables from the parent function within the lambda.
Flexibility: Lambdas can be passed as arguments to other functions, making them handy for functions like std::for_each, std::sort, etc.

How to create a lambda function?

We can use the following syntax to create lambda function:

A capture clause in a lambda function allows you to specify which variables from the surrounding scope (outside the lambda function) can be accessed and used within the lambda function. There are 3 commonly types of capture clauses:

Capture Nothing []: The lambda function cannot access any variables from the surrounding scope.
Capture Specific Variables by Value [var1, var2, ...]: The lambda function can access specific variables from the surrounding scope by value.
Capture Specific Variables by Reference [&var1, &var2, ...]: The lambda function can access specific variables from the surrounding scope by reference.

main


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#include <iostream>

int main()
{
    int multiplier = 2;
    
    // Lambda function capturing 'multiplier' by reference and with explicit return type (int)
    int result = [&multiplier](int num) -> int {
        return num * num * multiplier;
    }(5); // Invoking the lambda with argument 5
    
    std::cout << "Result: " << result << std::endl;
}

The function is constructed as follows:

The lambda function captures multiplier variable by reference [&multiplier].
The return type -> int specifies that the lambda function returns an integer.
The lambda is immediately invoked with the argument 5, and the result is stored in the result variable.

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Seção 4. Capítulo 4