is_imp : term -> bool
- SYNOPSIS
-
Tests a term to see if it is an implication or a negation.
- DESCRIBE
-
If M has the form t1 ==> t2, or the form ~t, then is_imp M
returns true. If the term is neither an implication nor a negation
the result is false.
- FAILURE
-
Never fails.
- COMMENTS
-
Yields true of negations because dest_imp destructs negations (for
backwards compatibility with PPLAMBDA). Use is_imp_only if you don't want
this behaviour.
- SEEALSO mk_imp,
dest_imp,
is_imp_only,
dest_imp_only
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