Exception parsing query with non-alphanumeric predicate name.

[s-webber]

Current (incorrect) behaviour when the predicate name is the same as an infix operator:

?- X = +(1,1).

Error parsing query:
Expected . but got: ,(1, 1) after: ?-(=(X, +))
?-X = +(1,1).
           ^

Current (incorrect) behaviour when the predicate name is not the same as an infix operator:

?- X = ~(1,1).

Error parsing query:
invalid command: ~(
?-X = ~(1,1).
       ^

Correct behaviour:

?- X = +(1, 1).

X = 1 + 1

yes (0 ms)

Note: it does currently work if the predicate name is quoted (e.g. ?- X = '+'(1,1).).

[s-webber]

Previous commit deals with queries of form ?- X = ~(1,1). (i.e. where predicate name is not also the name of an infix operator).

Reopening as still work required to parse queries like ?- X = +(1,1).