enum type_form {
    type_var,
    type_name,
    tuple_type,
    func_type,
};

struct type;

/* A Linked list of types */
struct type_list {
    struct type *elem;
    struct type_list *next;
};

struct func_type {
    struct type *dom;
    struct type *cod;
};

struct type_name {
    struct type_list *params;
    char *name;
};

struct type {
    enum type_form form;
    union {
        char *var_name;
        /* We represent a tuple with the linked list of its type components */
        struct type_list *tuple;
        struct func_type func;
        struct type_name type_name;
    };
};

/* type constructors and destructors */
struct type *make_tuple_type(struct type_list *t);
struct type *make_func_type(struct type *dom, struct type *cod);
struct type *make_var_type(char *name);
struct type *make_type_name(struct type_list *params, char *name);

void free_type(struct type *t);

/* type_list operations */
void free_type_list(struct type_list *l);

struct type_list_builder {
    struct type_list *head;
    struct type_list *last;
};

void type_list_append(struct type_list_builder *b, struct type *elem);