I have this function that checks a list of parsers if they work or not. I get error: EQUALO LPAREN FN. Any help?
fun oneOf [] = fn inp => NONE
| oneOf (p::ps) = (fn inp => case parse p inp of
NONE => oneOf ps inp
| SOME (v,out) => SOME (v,out))
A function defined with fn can have multiple cases just like a function defined with fun. So you can write something like fun pat1 => exp1 | pat2 => exp2. This means that when the SML parser sees the | at the beginning of line 2, it assumes that it belongs to the fn on line 1, not to the fun (because the fn came more recently). So when it reaches the =, it's confused because it expected a =>.
To fix your issue surround the fn on line 1 with parentheses.
