我可以在C中获得“宏多态性”吗？

概述我所追求的多态性类型是这样的： 假设我有一个名为draw()的宏,我有2个结构,一个叫做圆圈,另一个叫做方形.有可能以某种方式做这样的事情： #define draw() // can I get the text that's behind the macro?//then maybe, with _Generic achieve this?void draw_circle(struct 我所追求的多态性类型是这样的：

假设我有一个名为draw()的宏,我有2个结构,一个叫做圆圈,另一个叫做方形.有可能以某种方式做这样的事情：

#define draw() // can I get the text that's behind the macro?//then maybe,with _Generic achIEve this?voID draw_circle(struct circle);voID draw_square(struct square);struct circle c;struct square s;c.draw();//draw is a macro. this time it is supposed to expand to draw_circle(c);s.draw();//supposed to expand to draw_square(s);

EDIT_1：在阅读完答案之后,这是我到目前为止所做的.

//raw_array.h#pragma once#include <stdint.h>#include <stdlib.h>#define byte uint8_t#define _GET_OVERRIDE(_1,_2,_3,name,...) name/*#define init_impl(...) _GET_OVERRIDE(__VA_ARGS__,\    init_impl3,init_impl2,init_impl1)(__VA_ARGS__)#define init( name,... ) (raw_array * (name); init_impl( (name),__VA_ARGS__))*/#define array_init_impl(...) _GET_OVERRIDE(__VA_ARGS__,init_array_impl3,init_array_impl2,init_array_impl1)(__VA_ARGS__)///<summary>creates a variable of type raw_array with name as an IDentifIEr,and initializes based on the parameters</summary>#define RAW_ARRAY( name,... ) raw_array (name); array_init_impl( (&name),__VA_ARGS__)typedef struct indexable_memory_block_struct{    raw_array * _self;    byte * bytes;    size_t element_size;    size_t number_of_elements;} raw_array;///<summary>starts the an empty raw_array. only element_size is set.</summary>///<param name=r_arr>the raw_array to be initialized</param>///<param name=element_size>the size of the elements in this raw_array</param>voID init_impl1 ( raw_array * r_arr,size_t element_size ){    r_arr = malloc ( sizeof ( raw_array ) );    r_arr->element_size = element_size;    r_arr->number_of_elements = 0;    r_arr->bytes = NulL;    r_arr->_self = r_arr;}///<summary>///starts the raw_array an empty. byte with its bytes allocated///to their default value (0).///</summary>///<param name=r_arr>the raw_array to be initialized</param>///<param name=element_size>the size of the elements in this raw_array</param>///<param name=number_of_elements>the number of elements in the array</param>voID init_impl2 ( raw_array * r_arr,size_t element_size,size_t number_of_elements ){    r_arr = malloc ( sizeof ( raw_array ) );    r_arr->element_size = element_size;    r_arr->number_of_elements = number_of_elements;    r_arr->bytes = calloc ( number_of_elements,element_size );    r_arr->_self = r_arr;}///<summary>///starts the raw_array copying its contents from a normal array.///</summary>///<param name=r_arr>the raw_array to be initialized</param>///<param name=arr>the normal C array whose contents will be copIEd to this raw_array</param>///<param name=element_size>the size of the elements in this    raw_array</param>///<param name=number_of_elements>the number of elements in the array</param>voID init_impl3 ( raw_array * r_arr,const voID * const arr,size_t size_of_element,size_t number_of_elements ){    r_arr->bytes = malloc ( size_of_element * number_of_elements );    memcpy ( r_arr->bytes,arr,size_of_element * number_of_elements );    r_arr->element_size = size_of_element;    r_arr->number_of_elements = number_of_elements;    r_arr->_self = r_arr;}

还有其他部分,但这些是目前移植到这种新语法的部分.现在主要：

int main ( int argc,char * argv[] ){    int data[30];    //line bellow has a compilation error: *expected a ')'*    init ( r_arr,data,sizeof ( int ),30 );}

什么意思预期’)’
你们可以查看宏语法吗？
关于_Generic,我今天学到了它,如果它有用的话,我肯定会使用它.

EDIT_2：发现严重错误,将修复它并再次编辑. Visual Studio正在更新(12GB ……)所以我目前无法构建任何东西. [迷你编辑]：我猜我至少修正了粗错误. [迷你编辑]我的代码中另一个非常奇怪的错误,我将名称标记字符串化,是吗？！现在纠正了.

EDIT_3：已经睡觉并且VS再次运行,我修复了宏,将编辑它们并注释掉错误的代码.现在我需要circle.draw()行为……任何想法？

解决方法 除了@lirooPIErre的方法,你还可以使用C11 Generics.是的你没听错,C现在有仿制药.

考虑这个例子：

#include <stdio.h>#define draw(X) _Generic((X),\        struct circle: draw_circle,\        struct square: draw_square \        )(X)struct circle{};struct square{};voID draw_circle(struct circle a){    printf("Drawing a circle\n");}voID draw_square(struct square a){    printf("Drawing a square\n");}int main(voID){    struct square a;    draw(a);  // "Drawing a square"}

但即使它应该是便携式的,但遗憾的是它不是. M $编译器没有实现它们,但是clang和gcc这样做.

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