多态性(C语言) [英] Polymorphism (in C)
问题描述
可能重复:结果
我如何可以模拟OO风格多态性C 2
我想更好地了解基因多态性与我知道的例子语言的想法;
有多态性用C?
I'm trying to better understand the idea of polymorphism with examples from languages I know; is there polymorphism in C?
推荐答案
这是 Nekuromento的第二个例子,考虑在内,我认为习惯了面向对象的C方式:
This is Nekuromento's second example, factored in the way I consider idiomatic for object-oriented C:
#ifndef ANIMAL_H_
#define ANIMAL_H_
struct animal
{
// make vtable_ a pointer so they can be shared between instances
// use _ to mark private members
const struct animal_vtable_ *vtable_;
const char *name;
};
struct animal_vtable_
{
const char *(*sound)(void);
};
// wrapper function
static inline const char *animal_sound(struct animal *animal)
{
return animal->vtable_->sound();
}
// make the vtables arrays so they can be used as pointers
extern const struct animal_vtable_ CAT[], DOG[];
#endif
cat.c
#include "animal.h"
static const char *sound(void)
{
return "meow!";
}
const struct animal_vtable_ CAT[] = { { sound } };
dog.c
#include "animal.h"
static const char *sound(void)
{
return "arf!";
}
const struct animal_vtable_ DOG[] = { { sound } };
的main.c
#include "animal.h"
#include <stdio.h>
int main(void)
{
struct animal kitty = { CAT, "Kitty" };
struct animal lassie = { DOG, "Lassie" };
printf("%s says %s\n", kitty.name, animal_sound(&kitty));
printf("%s says %s\n", lassie.name, animal_sound(&lassie));
return 0;
}
这是运行时多态性的例子当方法解析碰巧的。
This is an example of runtime polymorphism as that's when method resolution happens.
C1X增加通用的选择,这使得通过宏可能编译时多态。下面的例子是从C1X四月草案采取部分6.5.1.1§5:
C1x added generic selections, which make compile-time polymorphism via macros possible. The following example is taken from the C1x April draft, section 6.5.1.1 §5:
#define cbrt(X) _Generic((X), \
long double: cbrtl, \
default: cbrt, \
float: cbrtf \
)(X)
数学函数型通用宏已经可以在C99通过头 tgmath.h
,但没有办法让用户自己定义的宏,而无需使用编译器扩展。
Type-generic macros for math functions were already available in C99 via the header tgmath.h
, but there was no way for users to define their own macros without using compiler extensions.
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