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C The function parameter passing method affects the implementation of the collection class library. There are three passing methods: passing value (copy), passing reference (direct access to the original variable) and passing pointer (indirect access to the original variable). Collection class libraries usually use passing references or pointers to optimize performance and safety. For example, STL containers use passing references to avoid copy overhead. In specific applications, the delivery method should be selected based on whether the function needs to modify the container, and the trade-off between performance and memory overhead should be considered.
C The relationship between the function parameter passing method and the collection class library
In C, the function parameter passing method affects the collection Class library implementation. Different delivery methods have effects on performance, security, and other aspects.
Transfer method
There are three function parameter transfer methods in C:
Applications in collection libraries
Collection libraries usually use different delivery methods to optimize performance and security:
Standard Template Library (STL): Containers such as
vector
and deque
are usually passed by reference. Pass an iterator to avoid copy overhead. Associative containers such as map
and set
access keys and values by passing references to maintain the association between elements. boost library:
boost::optional
and boost:: Smart pointer types such as variant
use pass-by-reference to access the underlying value. Practical case
Suppose we have a function that processes a collection of integersprocess_ints
:
void process_ints(vector<int>& numbers) { for (int& num : numbers) { num += 1; } }
numbers
container of process_ints
. Changes in the function do not affect the original container. vector<int> numbers = {1, 2, 3}; process_ints(numbers); // 原始容器仍为 {1, 2, 3}
numbers
container. Changes in the function are reflected on the original container. vector<int>& numbers = {1, 2, 3}; process_ints(numbers); // 原始容器变为 {2, 3, 4}
numbers
container is essentially the same as passing a reference. vector<int>* numbers = new vector<int>{1, 2, 3}; process_ints(*numbers); // 原始容器变为 {2, 3, 4}
Choose the appropriate passing method
Choosing the appropriate parameter passing method depends on the specific situation:
By understanding the relationship between function parameter passing methods and collection class libraries, you can optimize code performance and enhance security.
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