lambda function怎么用
时间: 2023-09-13 13:02:45 浏览: 55
Lambda函数是一种匿名函数,可以在需要函数的任何地方定义和使用它。以下是一个简单的示例:
```
# 定义一个lambda函数,它接受两个参数并返回它们的和
sum = lambda x, y: x + y
# 使用lambda函数
result = sum(3, 4)
print(result) # 输出结果为7
```
在上面的例子中,我们定义了一个lambda函数,它将两个参数相加并返回它们的和。我们可以使用这个函数来计算3和4的和。
Lambda函数通常用于需要一个简单的函数来执行一些特定任务的场景,而不需要定义一个完整的函数。它们通常用于函数式编程和高阶函数中。
相关问题
what is the lambda function in CPP
In C++, a lambda function is an anonymous function that can be defined inline with the rest of your code. It allows you to create a function object on the fly, without having to define a separate function. Lambda functions can capture variables from the surrounding context and can be passed around like any other object. Here's an example of a lambda function in C++:
```
#include <iostream>
#include <vector>
#include <algorithm>
int main() {
std::vector<int> nums{3, 6, 2, 7, 1, 9};
// Sort the vector in descending order using a lambda function
std::sort(nums.begin(), nums.end(), [](int a, int b) {
return a > b;
});
// Print the sorted vector
for (int num : nums) {
std::cout << num << " ";
}
return 0;
}
```
In this example, the lambda function is used as the third argument to the `std::sort` algorithm. The function takes two integers as arguments and returns `true` if the first argument is greater than the second argument, indicating that the vector should be sorted in descending order.
what is the cpature in CPP lambda function
In C++ lambda functions, the capture clause allows you to specify which variables from the surrounding context are accessible inside the lambda body.
There are two types of captures in C++ lambda functions:
- Value capture: It captures the value of the variable at the time of the lambda creation
- Reference capture: It captures the reference to the variable, allowing the lambda to modify the original variable.
The capture clause comes after the parameter list and before the function body in the lambda function declaration. It is enclosed in square brackets ([]), which can be followed by either an equal sign (=) or an ampersand (&).
Here is an example of a lambda function that captures a variable by value:
```
#include <iostream>
int main() {
int x = 5;
auto lambda = [x]() {
std::cout << "x = " << x << std::endl;
};
lambda(); // Output: x = 5
return 0;
}
```
In this example, the variable `x` is captured by value in the lambda function by including it in the capture clause ([]). The lambda function copies the value of `x` at the time of creation and stores it in its own internal state. When the lambda is called, it prints the value of `x`. The output is `x = 5`, which is the value of `x` at the time of the lambda creation.
Here is an example of a lambda function that captures a variable by reference:
```
#include <iostream>
int main() {
int x = 5;
auto lambda = [&x]() {
std::cout << "x = " << x << std::endl;
x = 10;
};
lambda(); // Output: x = 5
std::cout << "x = " << x << std::endl; // Output: x = 10
return 0;
}
```
In this example, the variable `x` is captured by reference in the lambda function by including it in the capture clause ([]). The lambda function stores a reference to the variable `x` in its internal state, allowing it to modify the original variable. When the lambda is called, it prints the value of `x`, which is `5`. The lambda function also modifies `x` to `10`. After the lambda is called, the value of `x` is printed, which is `10`.
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