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typedef struct Visitor {
Tokens tokens;
size_t current;
} Visitor;
Token
peek_token(const Visitor *visitor) {
return visitor->tokens.buf[visitor->current];
}
Token
next_token(Visitor *visitor) {
return visitor->tokens.buf[visitor->current++];
}
bool
has_next_token(const Visitor *visitor) {
return visitor->current < visitor->tokens.size;
}
Object *
parse_fixnum(Token tok) {
ssize_t num = 0;
int sign = 1;
for (size_t i = 0; i < tok.value.n; i++) {
char c = tok.value.start[i];
if (c == '-') {
sign = -1;
continue;
}
num = num * 10 + (c - '0');
}
return make_fixnum(num * sign);
}
Object * parse_tree(Visitor *vs);
Object *
parse_list(Visitor *vs) {
Token tok = peek_token(vs);
if (tok.type == TOKEN_EOF) {
return obj_err;
}
Object *next_obj = parse_tree(vs);
if (next_obj == obj_err) {
return obj_err;
}
Object *root = make_pair(next_obj, obj_nil);
Object *list = root;
while (has_next_token(vs)) {
Token tok = peek_token(vs);
if (tok.type == TOKEN_RPAREN) {
next_token(vs);
break;
}
if (tok.type == TOKEN_EOF) {
free_objects(root);
return obj_err;
}
next_obj = parse_tree(vs);
if (next_obj == obj_err) {
free_objects(root);
return obj_err;
}
list->cdr = make_pair(next_obj, obj_nil);
list = list->cdr;
}
return root;
}
Object *
parse_tree(Visitor *vs) {
Token tok = next_token(vs);
switch (tok.type) {
case TOKEN_FIXNUM: {
return parse_fixnum(tok);
} break;
case TOKEN_TRUE: {
return obj_true;
} break;
case TOKEN_FALSE: {
return obj_false;
} break;
case TOKEN_RPAREN: {
error_push((Error){
.type = ERR_TYPE_PARSER,
.value = ERR_UNBALANCED_PAREN,
.line = tok.line,
.col = tok.column,
});
return obj_err;
} break;
case TOKEN_QUOTE: {
// TODO: Implement.
error_push((Error){
.type = ERR_TYPE_PARSER,
.value = ERR_NOT_IMPLEMENTED,
.line = tok.line,
.col = tok.column,
});
return obj_err;
} break;
case TOKEN_LPAREN: {
Object *obj = parse_list(vs);
if (obj == obj_err) {
error_push((Error){
.type = ERR_TYPE_PARSER,
.value = ERR_UNBALANCED_PAREN,
.line = tok.line,
.col = tok.column,
});
}
return obj;
} break;
case TOKEN_STRING: {
Object *obj = make_string();
append_string(obj, tok.value);
return obj;
} break;
case TOKEN_SYMBOL: {
return make_symbol(tok.value);
} break;
case TOKEN_EOF: {
error_push((Error){
.type = ERR_TYPE_PARSER,
.value = ERR_EOF_REACHED,
.line = tok.line,
.col = tok.column,
});
return obj_err;
} break;
case TOKEN_NIL: {
return obj_nil;
} break;
default: {
break;
} break;
}
error_push((Error){
.type = ERR_TYPE_PARSER,
.value = ERR_EOF_REACHED,
.line = tok.line,
.col = tok.column,
});
return obj_err;
}
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