func parse(l *lexer.Lexer) (VValue, bool) {
token := l.Next()
switch token.Type {
case "symbol":
return VSym(token.Token), true
case "string":
return VStr(token.Token), true
case "number":
num, err := strconv.ParseFloat(token.Token, 64)
if err != nil {
panic(fmt.Sprintf("Invalid Number \"%s\"", token.Token))
}
return VNum(num), true
case "special":
return parse_special(token.Token), true
case ";":
parse(l)
return parse(l)
case "EOF":
return nil, false
case "(":
return parse_list(l)
default:
panic(fmt.Sprintf("Unexpected Token \"%s\"", token.Token))
}
return nil, false
}
func parse_list(l *lexer.Lexer) (VValue, bool) {
token := l.Peek()
switch token.Type {
case ")":
l.Next()
return VNil, true
case "EOF":
return nil, false
case ".":
l.Next()
return parse(l)
}
if car, ok := parse(l); ok {
if cdr, ok := parse_list(l); ok {
if _, ok := cdr.(*VPair); !ok {
if l.Next().Type != ")" {
panic("Can't have multiple cdr expressions")
}
}
return &VPair{car, cdr}, true
}
}
return nil, false
}