c++ - 复杂的 C 声明

Question

我刚刚在网上浏览了一些代码，发现了这个:

float * (*(*foo())[SIZE][SIZE])()

如何阅读此声明？阅读此类复杂的声明是否有一套特定的规则？

Answer 1

我有一段时间没有这样做了!

从foo开始往右走。

float * (*(*foo())[SIZE][SIZE])()

foo is a function with no arguments...

因为有右括号，所以不能正确。向左走:

float * (*(* foo())[SIZE][SIZE])()

foo is a function with no arguments returning a pointer

不能再往左走，所以让我们划掉括号再往右走

float * (*(* foo())[SIZE][SIZE])() float * (*(* foo())[SIZE][SIZE])() float * (*(* foo())[SIZE][SIZE])()

foo is a function with no arguments returning a pointer to an array of SIZE arrays of SIZE ...

到达右括号，再次向左到达指针符号:

float * (*(* foo())[SIZE][SIZE])()

foo is a function with no arguments returning a pointer to an array of SIZE arrays of SIZE pointers to ...

再次左括号，所以我们越过它并再次向右走:

float *( *(* foo())[SIZE][SIZE])() float *( *(* foo())[SIZE][SIZE])()

foo is a function with no arguments returning a pointer to an array of SIZE arrays of SIZE pointers to a function with no arguments...

从头到尾

_{float * ( *(* foo())[SIZE][SIZE])()}

foo is a function with no arguments returning a pointer to an array of SIZE arrays of SIZE pointers to a function with no arguments returning a pointer to float

---

而写的人，请教他使用typedef:

// Function that returns a pointer to float
typedef float* PFloatFunc ();

// Array of pointers to PFloatFunc functions
typedef PFloatFunc* PFloatFuncArray2D[SIZE][SIZE];

// Function that returns a pointer to a PFloatFuncArray2D
PFloatFuncArray2D* foo();