What are the precautions for using reference parameters of C++ functions?

Reference parameters in C allow a function to directly modify the parameters of the calling function, by passing a reference to the original value rather than a copy. Notes include: reference parameters must refer to valid objects and cannot refer to temporary objects. Modifications to reference parameters will affect the original variables, and it is necessary to distinguish between const references (which can only be read) and ordinary references.

Reference parameters of C functions: Notes

In C, reference parameters are a way to pass function parameters. It allows functions to modify the parameters of the calling function. Unlike passing by value, passing by reference does not create a copy of the parameter but operates directly on the original value.

Note:

• The reference parameter must refer to a valid object. The referenced object must already exist and be initialized before the function is called. Referring to an uninitialized object causes undefined behavior.
• Cannot reference temporary objects. Temporary objects are destroyed immediately after the function call and therefore cannot be referenced.
• Modifications to reference parameters will affect the original variables. Since pass-by-reference accesses the original value directly, any modifications to the reference parameters will be reflected on the original variable.
• Distinguish between const quotes and ordinary references. ** const A reference can only read the original value, not modify it.

Practical case:

Exchange two integers:

void swap(int& a, int& b) {
  // 交换两个数
  int temp = a;
  a = b;
  b = temp;
}

This function uses reference parameters a and b to modify the original variable.

Note:

• Since swap is a generic function, it can work on any integer type and does not have to be specific to Write separate functions for each type.
• References as function parameters allow the original variable to be modified by reference, thus avoiding the overhead of passing by value and additional memory allocation.

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