-fun validUser s =
- size s > 0 andalso size s < 50 andalso List.all
- (fn ch => isIdent ch orelse ch = #"." orelse ch = #"_" orelse ch = #"-" orelse ch = #"+")
- (String.explode s)
+fun validUsername name =
+ size name <= 12
+ andalso size name > 0
+ andalso Char.isLower (String.sub (name, 0))
+ andalso CharVector.all Char.isAlphaNum name