I am writing the parser for first-order conditions. I am using Scala and the scala-parser-combinators library. It works well, but I discovered this issue.

Here, I report the clause for negation (example: not predicate(p1)). It uses recursion, calling fol_condition, i.e. the root level rule for fol conditions:

 def fol_condition: Parser[FOLNature] = fol_negation | fol_predicate | ...
 def fol_negation : Parser[Negation] = "not"~fol_condition ^^ {case _~sub => Negation(sub)}
 def fol_predicate : Parser[Predicate] = ident~"("~repsep(logic_term,",")~")"^^ {case id~_~args~_ => Predicate(id,args)}
....

So, a string like "not predicate(p1)" produces the correct result Negation(Predicate("predicate",...)) However, when I parse a string like "note(p2)", it should produce a Predicate("note",...); instead, it returns Negation(Predicate(a,...)). In other words, the parser ignores whether there is a space between "not" and the following fol_condition.

This is not the desired behaviour. I would inform the parser that "not a" is different from "nota" because there is a space in between.