func (a *Atomiser) ReadList() (c *chain.Cell) {
var tail *chain.Cell
for a.NextToken(); !a.IsListEnd(); {
if a.IsEOF() {
panic("Unexpected EOF in list literal")
}
if c == nil {
c = &chain.Cell{Head: a.Read()}
tail = c
} else {
tail.Append(a.Read())
tail = tail.Tail
}
}
a.NextToken()
return
}
func parseId(expr *chain.Cell) (Condition, error) {
if expr == nil {
return nil, fmt.Errorf("missing ID value in (id) expression")
}
id := new(Id)
if id_str, ok := expr.Car().(atomiser.Symbol); !ok {
return nil, fmt.Errorf("expected ID, got '%#v' instead", expr.Car())
} else {
parsed_id, err := strconv.ParseInt(string(id_str), 10, 64)
if err != nil {
return nil, fmt.Errorf("couldn't parse numeric ID in id expression")
}
*id = Id(parsed_id)
}
return id, nil
}
func parseEqual(expr *chain.Cell) (Condition, error) {
cond := &Equals{}
if expr == nil {
return nil, errors.New("missing arguments in eq")
}
if field, ok := expr.Car().(atomiser.Symbol); !ok {
return nil, fmt.Errorf("expected field name, got '%#v' instead", expr.Car())
} else {
cond.Field = string(field)
}
expr = expr.Cdr()
if expr == nil {
return nil, fmt.Errorf("missing value in (eq %s) expression", cond.Field)
}
cond.Value = fmt.Sprintf("%v", expr.Car())
return cond, nil
}
func parseExpressionToCondition(expr *chain.Cell) (Condition, error) {
sym, ok := expr.Car().(atomiser.Symbol)
if !ok {
return nil, fmt.Errorf("expected symbol, got '%v' instead", expr.Car())
}
sym = atomiser.Symbol(strings.ToLower(string(sym)))
switch sym {
case "and":
return parseAnd(expr.Cdr())
case "or":
return parseOr(expr.Cdr())
case "eq":
return parseEqual(expr.Cdr())
case "id":
return parseId(expr.Cdr())
}
return nil, fmt.Errorf("unknown symbol '%s'", sym)
}