struct type;
struct expr;
struct pattern_list;

struct value_decl {
    char *name;
    struct expr *body;
};

/* List of function definition clauses */
struct func_decl_list {
    char *name;
    struct pattern_list *args;
    struct expr *body;

    struct func_decl_list *next;
};

struct func_decl_list_builder {
    struct func_decl_list *head;
    struct func_decl_list *last;
};

void func_decl_list_append(struct func_decl_list_builder *b, char *name, struct pattern_list *args, struct expr *body);
void free_func_decl_list(struct func_decl_list *l);

/* A list of type variables */
struct var_list {
    char *name;
    struct var_list *next;
};

struct var_list_builder {
    struct var_list *head;
    struct var_list *last;
};

void var_list_append(struct var_list_builder *b, char *elem);
void free_var_list(struct var_list *l);

/* List of datatype constructors */
struct constructor_list {
    char *name;
    struct type *t;
    struct constructor_list *next;
};

struct constructor_list_builder {
    struct constructor_list *head;
    struct constructor_list *last;
};

void constructor_list_append(struct constructor_list_builder *b, char *name, struct type *t);
void free_constructor_list(struct constructor_list *l);

struct datatype_decl {
    /* Definition parameters */
    struct var_list *type_params;
    /* datatype name */
    char *name;
    /* Datatype constructors list */
    struct constructor_list *ctors;
};

struct alias_decl {
    struct var_list *type_params;
    char *definiendum;
    struct type *definiens;
};

struct typecheck_decl {
    char *name;
    struct type *t;
};

enum decl_form {
    value_decl,
    func_decl,
    datatype_decl,
    alias_decl,
    typecheck_decl,
};

struct decl {
    enum decl_form form;
    union {
        struct value_decl value;
        struct func_decl_list *func;
        struct datatype_decl datatype;
        struct alias_decl alias;
        struct typecheck_decl typecheck;
    };
};

struct decl_list {
    struct decl *elem;
    struct decl_list *next;
};

struct decl_list_builder {
    struct decl_list *head;
    struct decl_list *last;
};

void decl_list_append(struct decl_list_builder *b, struct decl *elem);
void free_decl_list(struct decl_list *l);

struct decl *make_value_decl(char *name, struct expr *body);
struct decl *make_func_decl(struct func_decl_list *f);
struct decl *make_datatype_decl(struct var_list *ps, char *name, struct constructor_list *cs);
struct decl *make_alias_decl(struct var_list *ps, char *def, struct type *body);
struct decl *make_typecheck_decl(char *n, struct type *t);

void free_decl(struct decl *d);