带有指针参数ANSI C的函数

Question

我尝试了许多不同的方法-似乎没有一个是正确的方法...

我想向上，向下，向左，向右传递指针，以便可以在调用的函数中更改它们的值。 我不知何故找不到正确的语法。 而且我也找不到它-就像我确实尝试了在教科书和网上找到的建议一样，但是...没有运气。

//long find_neighbours( long, long *up, long *down, long *left, long *)
long find_neighbours( long, long, long, long, long);                  
int main (int argc, char *farg[])
{
    ...
    neighbours = find_neighbours(i, &up, &down, &left, &right);
    ...
}

//long find_neighbours( long center_number, long *up, long *down, long *right) 

long find_neighbours( long, long, long, long, long)
long center_number, *up, *down, *left, *right;
{
long x, y, neighbours;
 y = (long)(center_number/Lmax);
 x = center_number - (y*Lmax);

 if( !( x % center_number) ) //lqwa stena
 {
     *left = center_number + Lmax;
     *right = center_number+1;
 }   
 else
 {
    if( !((x+1)%center_number) ) //dqsna stena
    {
        *left = center_number-1;
        *right = center_number-Lmax;
    }
    else
    {   
        *left = center_number - 1;
        *right = center_number + 1;
    }
 }   

 if( y == 0 ) //lqwa stena
 {
     *up = 1 + x;
     *down = Lmax1 + x;
 }
 else
 {   
    if( y == Lmax1 ) //dqsna stena
    {
        *up = x;
        *down = Lmax - 2 +x;
    }
    else
    {   
        *down = center_number - Lmax;
        *up = center_number + Lmax;  
    }
 }   

 neighbours = Numb[*left] + Numb[*right] + Numb[*up] + Numb[*down];

 return (neighbours);
}


>>>$ gcc -lm perco_concCyclingv2.c -o square_clusters

>>>perco_concCyclingv2.c: In function ‘main’:
>>>perco_concCyclingv2.c:183:20: warning: passing argument 2 of ‘find_neighbours’ makes >>>integer from pointer without a cast [enabled by default]
>>>                    neighbours = find_neighbours(i, &up, &down, &left, &right);
 >>>                   ^
>>>perco_concCyclingv2.c:20:6: note: expected ‘long int’ but argument is of type ‘long int >>>**’
>>> long find_neighbours( long, long, long, long, long);
>>>      ^
>>>perco_concCyclingv2.c:183:20: warning: passing argument 3 of ‘find_neighbours’ makes >>>integer from pointer without a cast [enabled by default]
>>>                    neighbours = find_neighbours(i, &up, &down, &left, &right);
>>>                    ^
>>>perco_concCyclingv2.c:20:6: note: expected ‘long int’ but argument is of type ‘long int >>>**’
>>> long find_neighbours( long, long, long, long, long);
>>>      ^
>>>perco_concCyclingv2.c:183:20: warning: passing argument 4 of ‘find_neighbours’ makes >>>integer from pointer without a cast [enabled by default]
>>>                    neighbours = find_neighbours(i, &up, &down, &left, &right);
>>>                    ^
>>>perco_concCyclingv2.c:20:6: note: expected ‘long int’ but argument is of type ‘long int >>>**’
>>> long find_neighbours( long, long, long, long, long);
>>>      ^
>>>perco_concCyclingv2.c:183:20: warning: passing argument 5 of ‘find_neighbours’ makes >>>integer from pointer without a cast [enabled by default]
>>>                    neighbours = find_neighbours(i, &up, &down, &left, &right);
>>>                   ^
>>>perco_concCyclingv2.c:20:6: note: expected ‘long int’ but argument is of type ‘long int >>>**’
>>> long find_neighbours( long, long, long, long, long);
>>>      ^
>>>perco_concCyclingv2.c:235:21: warning: passing argument 2 of ‘find_neighbours’ makes >>>integer from pointer without a cast [enabled by default]
>>>                     neighbours = find_neighbours(i, &up, &down, &left, &right);
>>>                     ^
>>>perco_concCyclingv2.c:20:6: note: expected ‘long int’ but argument is of type ‘long int >>>**’
>>> long find_neighbours( long, long, long, long, long);
>>>      ^
>>>perco_concCyclingv2.c:235:21: warning: passing argument 3 of ‘find_neighbours’ makes >>>integer from pointer without a cast [enabled by default]
>>>                     neighbours = find_neighbours(i, &up, &down, &left, &right);
>>>                     ^
>>>perco_concCyclingv2.c:20:6: note: expected ‘long int’ but argument is of type ‘long int >>>**’
>>>long find_neighbours( long, long, long, long, long);
>>>      ^
>>>perco_concCyclingv2.c:235:21: warning: passing argument 4 of ‘find_neighbours’ makes >>>integer from pointer without a cast [enabled by default]
>>>                     neighbours = find_neighbours(i, &up, &down, &left, &right);
>>>                     ^
>>>perco_concCyclingv2.c:20:6: note: expected ‘long int’ but argument is of type ‘long int >>>**’
>>> long find_neighbours( long, long, long, long, long);
>>>      ^
>>>perco_concCyclingv2.c:235:21: warning: passing argument 5 of ‘find_neighbours’ makes >>>integer from pointer without a cast [enabled by default]
>>>                     neighbours = find_neighbours(i, &up, &down, &left, &right);
>>>                     ^
>>>perco_concCyclingv2.c:20:6: note: expected ‘long int’ but argument is of type ‘long int >>>**’
>>> long find_neighbours( long, long, long, long, long);
>>>      ^
>>>perco_concCyclingv2.c: In function ‘find_neighbours’:
>>>perco_concCyclingv2.c:278:6: error: old-style parameter declarations in prototyped >>>function definition
>>> long find_neighbours( long, long, long, long, long)
>>>      ^
>>>perco_concCyclingv2.c:278:1: error: parameter name omitted
>>>long find_neighbours( long, long, long, long, long)
>>> ^
>>>perco_concCyclingv2.c:278:1: error: parameter name omitted
>>>perco_concCyclingv2.c:278:1: error: parameter name omitted
>>>perco_concCyclingv2.c:278:1: error: parameter name omitted
>>>perco_concCyclingv2.c:278:1: error: parameter name omitted
>>>perco_concCyclingv2.c:283:13: error: ‘center_number’ undeclared (first use in this >>>function)
>>>  y = (long)(center_number/Lmax);
>>>             ^
>>>perco_concCyclingv2.c:283:13: note: each undeclared identifier is reported only once >>>for each function it appears in
>>>perco_concCyclingv2.c:288:7: error: ‘left’ undeclared (first use in this function)
>>>      *left = center_number + Lmax;
>>>       ^
>>>perco_concCyclingv2.c:289:7: error: ‘right’ undeclared (first use in this function)
>>>      *right = center_number+1;
>>>       ^
>>>perco_concCyclingv2.c:307:7: error: ‘up’ undeclared (first use in this function)
>>>      *up = 1 + x;
>>>       ^
>>>perco_concCyclingv2.c:308:7: error: ‘down’ undeclared (first use in this function)
>>>      *down = Lmax1 + x;
>>>

请帮助...任何形式的？ 谢谢...

Answer 1

每当您需要一个函数来修改其参数时，请记住以下几点：

1. 声明函数，使其接受类型，指针（*）和变量的名称。
2. 在函数中，给变量赋前缀*。
3. 在函数的调用程序中，将变量传递给函数时，在变量前加上＆。

这是一个演示代码段。 它定义了一个将其参数设置为100的函数。然后，对一个值为0的变量调用此函数，并在调用后打印此变量的值，以表明确实对其进行了修改。

int f(int* x) {
    *x = 100;
}

int main(void) {
    int q = 0;
    f(&q);
    printf("%d\n", q);
    return 0;
}

我希望这有帮助。

Answer 2

谢谢-在阅读完所有内容后，我发现自己在做错事情，所有的事情我都没看过-唯一的错误是-甚至根本没有看我如何声明变量。 “因为它是如此简单”。

在“主要”中：

long *x, *y, left, right, up, down, xp, yp; // the right way

long *x, *y, *left, *right, *up, *down, *xp, *yp; // the way it was left... 

我对错误和警告完全感到困惑-从未回到声明行。

很抱歉花了您很多时间。 感谢大家。