How to perform lazy evaluation using C++ lambda expressions?

How to perform lazy evaluation using C lambda expressions? Create a lazily evaluated function object using a lambda expression. Delayed computation defers execution until needed. Calculate results only when needed, improving performance.

How to perform delayed evaluation using C lambda expressions

Delayed evaluation means delaying the evaluation of the result of an expression until Calculate only when needed. This is useful in certain situations, such as when the expression is expensive to evaluate and the result is not needed in the first place.

Lambda expressions can be used in C to implement lazy evaluation. Lambda expressions are anonymous function objects that allow the creation of inline functions in code.

Grammar

The syntax of lambda expression is as follows:

[capture list] (parameter list) -> return type { function body }

• capture list: Specify lambda expression can Which external variables are accessed.
• parameter list: Specify any parameters received by the lambda expression.
• return type: Specifies the type returned by the lambda expression.
• function body: Specifies the code executed by the lambda expression.

Practical Example

Consider the following example, which demonstrates how to use lambda expressions to implement lazy evaluation:

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
  // 创建一个包含一些数字的向量
  std::vector<int> numbers = {1, 2, 3, 4, 5};

  // 使用 lambda 表达式创建延迟求值的函数对象
  auto square = [numbers](int number) {
    std::cout << "计算 " << number << " 的平方" << std::endl;
    return number * number;
  };

  // 打印每个数字的平方
  std::for_each(numbers.begin(), numbers.end(), square);

  return 0;
}

Output

计算 1 的平方
1
计算 2 的平方
4
计算 3 的平方
9
计算 4 的平方
16
计算 5 的平方
25

In this example, the square lambda expression is responsible for calculating the square of each number. However, the actual calculation is delayed until std::for_each is called. This means that the square is only calculated when needed, which can improve performance.

The above is the detailed content of How to perform lazy evaluation using C++ lambda expressions?. For more information, please follow other related articles on the PHP Chinese website!