为什么将指针(*)和数组([])符号绑定到变量名而不在变量声明中键入? [英] Why pointer (*) and array ([]) symbols are bound to variable name and not to type in variable declaration?

问题描述

关于C(和C ++的C子集)中的指针和数组声明的详细信息，关于SO的问题很多.
我对为什么感兴趣.
为什么当我们在一行中声明多个指针/数组时，必须在每个变量的前面放置*，[]吗?

There're a lot of questions on SO about details of pointer and array declarations in C (and C subset of C++).
I'm more interested in why.
Why do we have to put *, [] in front of every variable when we declare several pointers/arrays in a row?

int *a, *b;
int c[1], d[1];

为什么我们必须在函数指针中的变量名之后/周围输入内容?

Why do we have to type out things after/around variable names in function pointers?

void (*foo_ptr)(int, int);

为什么，当甚至编译器都将这些内容作为类型的一部分识别并报告时，我们具有使许多新手感到困惑的功能吗?例如:function foo accepts int** but it was given int*

Why do we have this feature that confuses a lot of newcomers, when even compilers recognize and report these things as part of type? Ex: function foo accepts int** but it was given int*

我想我正在寻找它背后的直觉，从而导致以这种方式创建它，以便可以将其应用于对语言的理解.现在我看不到...

I guess I'm looking for intuition behind it that caused it being created this way, so that I can apply it to my understanding of the language. Right now I just don't see it...

推荐答案

Kernighan和Ritchie用 C编程语言，1978年，第90页:

Kernighan and Ritchie write, in The C Programming Language, 1978, page 90:

指针px的声明是新的.

int *px;

用作助记符；它表示组合*px是int，也就是说，如果px出现在上下文*px中，则它等效于类型int的变量.实际上，变量声明的语法模仿了可能出现该变量的表达式的语法.这种推理在涉及复杂声明的所有情况下都是有用的.例如，

is intended as a mnemonic; it says the combination *px is an int, that is, if px occurs in the context *px, it is equivalent to a variable of the type int. In effect, the syntax of the declaration for a variable mimics the syntax of expressions in which the variable might appear. This reasoning is useful in all cases involving complicated declarations. For example,

double atof(), *dp;

表示在表达式atof()和*dp中具有类型double的值.

says that in an expression atof() and *dp have values of type double.

因此，我们看到，在诸如int X, Y, Z，X，Y和Z的声明中，为我们提供了表达式的图片"，例如b，*b，b[10] ，*b[10]等.声明的标识符的实际类型是从图片得出的:由于*b[10]是int，因此b[10]是指向int的指针，所以b是包含10个指向int的指针的数组.

Thus, we see that, in declarations such as int X, Y, Z, X, Y, and Z give us "pictures" of expressions, such as b, *b, b[10], *b[10], and so on. The actual type for the declared identifier is derived from the picture: Since *b[10] is an int, then b[10] is a pointer to an int, so b is an array of 10 pointers to int.

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