gistfile1.h

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

typedef struct PEOPLE {
    char name[25];
    struct PEOPLE *next;
} people;

struct Greeter {
    // methods
    struct Greeter* (*say)(void);
    struct Greeter* (*hello)(void);
    struct Greeter* (*good_bye)(void);
    struct Greeter* (*to)(const char*);
    struct Greeter* (*and)(const char*);
    void            (*end)(void);
    // fields
    char type[14];
    people *names;
} *greeter;

void            set_type(const char*);
struct Greeter* add_name(const char*);
struct Greeter* hello(void);
struct Greeter* good_bye(void);
void            end(void);

struct Greeter* initialize()
{
    if (greeter == NULL) {
        greeter = (struct Greeter*)malloc(sizeof(struct Greeter));
        greeter->say = initialize;
        greeter->hello = hello;
        greeter->good_bye = good_bye;
        greeter->to = add_name;
        greeter->and = add_name;
        greeter->end = end;

        people *root = (people*)malloc(sizeof(people));
        root->next = NULL;
        greeter->names = root;
    }
    return greeter;
}

void set_type(const char* type)
{
    strcpy(initialize()->type, type);
}

struct Greeter* add_name(const char* name)
{
    struct Greeter* gt = initialize();
    people *p;

    people *new = (people*)malloc(sizeof(people));
    strcpy(new->name, name);
    new->next = NULL;

    for (p = gt->names; p->next != NULL; p = p->next) {}
    p->next = new;

    return gt;
}

struct Greeter* hello()
{
    set_type("hello");
    return initialize();
}

struct Greeter* good_bye()
{
    set_type("good bve");
    return initialize();
}

void end()
{
    struct Greeter* gt = initialize();
    people *p, *root = gt->names;

    if (strcmp(gt->type, "") != 0)
        printf("%s, ", gt->type);
    for (p = root->next; p->next != NULL; p = root->next) {
        printf("%s and ", p->name);
        root->next = p->next;
        free(p);
    }
    printf("%s!\n", p->name);
    root->next = NULL;
    free(p);
    strcpy(gt->type, "");
}

int main(int argc, char *argv[])
{
    struct Greeter* me = initialize();

    me->say()->hello()->
        to("yaotti")->
        and("satzz")->
        and("hmsk")->
        end();

    me->say()->good_bye()->
        to("pole")->
        and("umemoto")->
        and("muraguchi")->
        end();

    me->and("tomohiro")->
        and("sixeight")->
        end();

    return 0;
}