谁能帮我解释一下这段代码吗？

Question

C code to demonstrate the use of function pointers.

#include<stdio.h>
struct geoobject
{
        enum{CIR=0,REC,TRG}gcode;
        union
        {
                struct cir{double x,y,r;}c;
                struct rec{double x,y,w,h;}r;
                struct trg{double x,y,b,h;}t;
        };
};
typedef void(*DrawFunc)(struct geoobject);

Typedefed function pointer.

void drawcir(struct geoobject go)
{
        printf("Circle:(%lf,%lf,%lf)\n",go.c.x,go.c.y,go.c.r);
}
void drawrec(struct geoobject go)
{
        printf("Rec:(%lf,%lf,%lf,%lf)\n",go.r.x,go.r.y,go.r.w,go.r.h);
}
void drawtrg(struct geoobject go)
{
        printf("Triangle:(%lf,%lf,%lf,%lf)\n",go.t.x,go.t.y,go.t.b,go.t.h);
}
DrawFunc DrawArr[]={drawcir,drawrec,drawtrg};
int main(void)
{
        struct geoobject go;
        go.gcode=CIR;
        go.c.x=2.3;go.c.y=3.6;go.c.r=1.2;
        DrawArr[go.gcode](go);
        go.gcode=REC;
        go.r.x=4.5;go.r.y=1.9;go.r.w=4.2;go.r.h=3.8;
        DrawArr[go.gcode](go);
        go.gcode=TRG;
        go.t.x=3.1;go.t.y=2.8;go.t.b=4.4;go.t.h=2.7;
        DrawArr[go.gcode](go);
        return 0;
}

Confused with typedef void(*DrawFunc)(struct geoobject) and its usage in the program.Please explain.

Answer 1

typedef void(*DrawFunc)(struct geoobject) 表示 Drawfunc 现在是指向函数的指针的 typdef(或名称/别名)，该函数采用struct geoobject 作为参数，并返回 void。

在程序中，声明了一个函数指针数组:

DrawFunc DrawArr[]={drawcir,drawrec,drawtrg};

所有三个函数drawcir()、drawrec() 和drawtrg() 均遵循typedef DrawFunc 的定义，并且可以使用别名。