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This article mainly introduces the C++ function parameter example analysis related knowledge, the content is detailed and easy to understand, the operation is simple and fast, has a certain reference value, I believe that everyone will have some gains after reading this C++ function parameter example analysis article, let's take a look at it.

Default values of function parameters

In C++, you can provide a default value for a parameter at function declaration time.

Default values are used when a function is called without providing a value for the parameter

Default values for parameters must be specified in the function declaration

Here is a code:

#include int mul(int x = 0);int main(int argc, char *argv[]){ printf("%d\n", mul()); printf("%d\n", mul(-1)); printf("%d\n", mul(2)); return 0;}int mul(int x){ return x * x;}

The following are the compilation results of the program in C++ and C language environments respectively:

In C++ compiler environment, the program can be compiled, but not in C language conditions, which shows that the default value of function parameters is an extension of C++ language to C language. And the default value of the function parameter will not be reported when it is defined, if it is placed in the function declaration, it will report an error.

Rules for default parameters of functions

Default values for parameters must be supplied from right to left

Function calls with default values, subsequent arguments must use default values

As follows:

Here's a code to feel:

#include int add(int x, int y = 0, int z = 0);int main(int argc, char *argv[]){ printf("%d\n", add(1)); printf("%d\n", add(1, 2)); printf("%d\n", add(1, 2, 3)); return 0;}int add(int x, int y, int z){ return x + y + z;}

The output is as follows:

II. Function placeholder parameters

In C++ you can provide placeholder parameters for functions

Placeholder parameters have only parameter type declarations and no parameter name declarations

Usually, in letters.| Placeholder parameters cannot be used inside the number volume

That is, the following notation is not problematic in C++:

The Meaning of Function Placeholder Parameters

Placeholder parameters are used in combination with default parameters

Possible irregularities in compatible C programs

For example, the following two expressions mean the same thing in C++, indicating no parameter input; while in C, the former indicates that the number of parameters that can be input is unlimited, while the latter indicates no parameter input.

Here is a code:

#include int func(int x, int = 0);int main(int argc, char *argv[]){ printf("%d\n", func(1)); printf("%d\n", func(2, 3)); return 0;}int func(int x, int){ return x;}

The following is the output of the code under C++ and C compilation conditions:

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