如何在函数参数中将结构指针变量设置为默认值NULL? [英] How do I set a structure pointer variable to default value NULL in a function parameter?

问题描述

struct queue{
    int value;
    struct queue *tlink;
    struct queue *blink;
};

typedef struct queue* Q;

void enqueue(Q top, int val, Q bottom=NULL);

错误:

error:

expected ‘;’, ‘,’ or ‘)’ before ‘=’ token
void enqueue(Q top, int val, Q bottom=NULL);

我尝试过的事情:

我正在尝试将结构指针变量初始化为函数参数中的默认值NULL. (默认参数)

What I have tried:

I am trying to initialise a structure pointer variable to default value NULL in function parameter. (Default parameter)

推荐答案

C没有默认参数的概念，因此您几乎不能这样做.


(请问，这是骗人的孩子，但它非常复杂和混乱: C默认参数-堆栈溢出 [ ^ ] -请参阅BK的解决方案，即TBH比维护POV最初的问题要差.)

C doesn''t have any concept of default parameters, so you pretty much can''t do that.


(Which is a lie-to-children, becuase you can, but it''s horribly complicated and messy: C default arguments - Stack Overflow[^] - see BK''s solution, which TBH is worse than the original problem from a maintenance POV).

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