Function parameter passing essentially determines how the function obtains and modifies external variables. Under pass-by-value, the function obtains a copy of the value of the incoming variable, and modifications to the copy do not affect the external variables; under pass-by-reference, the function directly receives the reference to the external variable, and modifications to the parameters also modify the external variables.
The essence and principle of function parameter passing
Introduction
In programming, function parameters Passing is a crucial concept that determines how functions obtain and modify external variables. In this article, we will delve into the nature and principles of function parameter passing, and deepen our understanding through practical cases.
How to pass function parameters
In different programming languages, the way to pass function parameters may be different. The following are the two most common ways of passing:
Practical example:
To understand function parameter passing, let us consider the following C code:
void increment(int n) { n++; } int main() { int x = 5; increment(x); cout << x; // 输出:5 }
In this example,increment
The function passes parameters by value.n
inside the function is a copy of the external variablex
. Modifications ton
will not affect the value ofx
. Therefore, thex
printed in themain
function is still 5.
Now, let us modify the code and change theincrement
function to pass by reference:
void increment(int& n) { n++; } int main() { int x = 5; increment(x); cout << x; // 输出:6 }
This time, theincrement
function uses pass by reference Pass parameters via pass.n
inside the function directly points to the external variablex
. Modifications ton
directly modify the value ofx
. Therefore, thex
printed in themain
function is 6.
Summary
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