[forwardchain].
'Command examples:       CHECK|: forwardchain.'.
'                        CHECK|: forwardchain h#3.'.
'                        CHECK|: forwardchain c#2.'.
''.
'This command attempts to use a hypothesis of the form "A -> B" (or'.
'"A <-> B" or "B <-> A") by proving that A holds and inferring that B'.
'holds in consequence.  If the first form of the command is used, the'.
'user is prompted to give a hypothesis or conclusion to be used.  If'.
'a hypothesis is given, it must be of one of the forms mentioned above.'.
'If a conclusion C is given, forward chaining will be applied to any'.
'hypothesis which would allow C to be inferred in this way.  Where'.
'there is more than one possibility, the user is prompted to decide'.
'what is required.'.
