首页 \ 问答 \ 在C / C ++中将指针(数组的名称)传递给函数(passing pointers (the name of array) into function in C/C++)

在C / C ++中将指针(数组的名称)传递给函数(passing pointers (the name of array) into function in C/C++)

比方说,我们创建一个数组,如:

int a[4]={1,2,3,4};

现在, a是该数组的名称,并且指针指向第一个元素a[0] 。 所以当我想调用数组中的元素时,我可以使用a[ i ]*(a+i)

现在我有一个功能:

void print_array(int* array, int arraySize){
    for(int i=0; i<arraySize; i++){
       cout<<*(array+i)<<endl;
       cout<<array[i]<<endl;
    }
}

当我使用print_array(a,4) a[4]={1,2,3,4}传递a[4]={1,2,3,4}此函数时,对于cout的第一行,我完全理解,因为我使用*(a+i)方法访问数据和a是我通过的指针。

我无法理解的是:因为我将一个指针传递给函数,为什么我可以使用a[i]的格式,比如cout的第二行? 不是一个指针? 如果a是一个指针,为什么a[i]工作?

这让我困惑了整整一天。 任何帮助都感激不尽!


Lets say we create an array like:

int a[4]={1,2,3,4};

Now a is the name of this array and also the pointer points to the first element a[0]. So when I want to call the elements in the array, I can use a[ i ] or *(a+i).

Now I have a function:

void print_array(int* array, int arraySize){
    for(int i=0; i<arraySize; i++){
       cout<<*(array+i)<<endl;
       cout<<array[i]<<endl;
    }
}

When I pass a[4]={1,2,3,4} into this function using print_array(a,4), for the first line of cout, I fully understand because I use *(a+i) method to access data and a is the pointer I passed.

What I can't understand is: since I pass a pointer a into function, why can I use a in the format of a[i] like the second line of cout? Isn't a a pointer? If a is a pointer why does a[i] work?

This has confused me for a whole day. Any help will be much appreciated!


原文:https://stackoverflow.com/questions/42203474
更新时间:2021-12-04 17:12

最满意答案

d3.csvParse返回一个数组,但是你在这里将它转换为一个字符串:

var data = JSON.stringify(d3.csvParse(data));

当然,字符串没有.map 。 你可能想遍历数组:

const newData = d3.csvParse(data);
newData.forEach((item, i) => console.log(`Hello ${item.col1} this ${item.col2} there are ${item.col3} blabla`));

(不要使用.map因为你没有把它转换成一个新的数组,至少不是你发布的代码)


d3.csvParse returns an array, but you convert it to a string here:

var data = JSON.stringify(d3.csvParse(data));

Strings don't have .map, of course. You probably want to iterate over the array:

const newData = d3.csvParse(data);
newData.forEach((item, i) => console.log(`Hello ${item.col1} this ${item.col2} there are ${item.col3} blabla`));

(don't use .map because you aren't transforming it into a new array, at least not in the code you've posted)

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