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typedef enum ObjectType {
OBJ_TYPE_FIXNUM,
OBJ_TYPE_BOOL,
OBJ_TYPE_NIL,
OBJ_TYPE_SYMBOL,
OBJ_TYPE_STRING,
OBJ_TYPE_PAIR,
OBJ_TYPE_PROCEDURE,
OBJ_TYPE_ERR,
} ObjectType;
struct Environment;
typedef struct Object {
ObjectType type;
union {
// OBJ_TYPE_FIXNUM
ssize_t fixnum;
// OBJ_TYPE_STRING
struct {
char *string;
size_t string_n;
};
// OBJ_TYPE_PAIR
struct {
struct Object *car;
struct Object *cdr;
};
// OBJ_TYPE_SYMBOL
struct {
char *symbol;
size_t symbol_n;
};
// OBJ_TYPE_PROCEDURE
struct Object *(*proc)(struct Environment *env, struct Object *args);
};
} Object;
//
// Singletons.
//
static Object *obj_nil;
static Object *obj_true;
static Object *obj_false;
static Object *obj_err;
//
// Constructors.
//
Object *
alloc_object(ObjectType type) {
Object *obj = malloc(sizeof(Object));
obj->type = type;
return obj;
}
Object *
make_fixnum(ssize_t num) {
Object *obj = alloc_object(OBJ_TYPE_FIXNUM);
obj->fixnum = num;
return obj;
}
Object *
make_procedure(Object *(*proc)(struct Environment *, struct Object *args)) {
Object *obj = alloc_object(OBJ_TYPE_PROCEDURE);
obj->proc = proc;
return obj;
}
Object *
make_pair(Object *car, Object *cdr) {
Object *obj = alloc_object(OBJ_TYPE_PAIR);
obj->car = car;
obj->cdr = cdr;
return obj;
}
Object *
make_symbol(StringView sv) {
Object *obj = alloc_object(OBJ_TYPE_SYMBOL);
obj->symbol = malloc(sizeof(char) * sv.n);
memcpy(obj->symbol, sv.start, sv.n);
obj->symbol_n = sv.n;
return obj;
}
Object *
make_string(void) {
Object *obj = alloc_object(OBJ_TYPE_STRING);
obj->string = NULL;
obj->string_n = 0;
return obj;
}
void
append_string(Object *obj, const StringView sv) {
assert(obj != NULL);
assert(obj->type == OBJ_TYPE_STRING);
if (sv.n == 0) {
return;
}
obj->string = realloc(obj->string, (obj->string_n + sv.n) * sizeof(char));
memcpy(obj->string + obj->string_n, sv.start, sv.n);
obj->string_n += sv.n;
}
void
free_objects(Object *root) {
switch (root->type) {
case OBJ_TYPE_BOOL: break;
case OBJ_TYPE_NIL: break;
case OBJ_TYPE_ERR: break;
case OBJ_TYPE_PROCEDURE:
case OBJ_TYPE_FIXNUM: {
free(root);
} break;
case OBJ_TYPE_SYMBOL: {
if (root->symbol != NULL) {
free(root->symbol);
}
free(root);
} break;
case OBJ_TYPE_STRING: {
if (root->string != NULL) {
free(root->string);
}
free(root);
} break;
case OBJ_TYPE_PAIR: {
if (root->car != NULL) {
free_objects(root->car);
}
if (root->cdr != NULL) {
free_objects(root->cdr);
}
free(root);
} break;
}
}
void display(Object *root);
void
display_pair(Object *root) {
display(root->car);
if (root->cdr->type == OBJ_TYPE_PAIR) {
printf(" ");
display_pair(root->cdr);
} else if (root->cdr == obj_nil) {
return;
} else {
printf(" . ");
display(root->cdr);
}
}
void
display(Object *root) {
switch (root->type) {
case OBJ_TYPE_FIXNUM: {
printf("%zd", root->fixnum);
} break;
case OBJ_TYPE_BOOL: {
if (root == obj_true) {
printf("true");
} else {
printf("false");
}
} break;
case OBJ_TYPE_NIL: {
printf("()");
} break;
case OBJ_TYPE_STRING: {
printf("\"%.*s\"", (int)root->string_n, root->string);
} break;
case OBJ_TYPE_SYMBOL: {
printf(":%.*s", (int)root->symbol_n, root->symbol);
} break;
case OBJ_TYPE_PAIR: {
printf("(");
display_pair(root);
printf(")");
} break;
case OBJ_TYPE_PROCEDURE: {
printf("#{procedure}");
} break;
case OBJ_TYPE_ERR: {
printf("#{error}");
} break;
}
return;
}
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