File: NOT_ELIM.doc

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\DOC NOT_ELIM

\TYPE {NOT_ELIM : (thm -> thm)}

\SYNOPSIS
Transforms {|- ~t} into {|- t ==> F}.

\KEYWORDS
rule, implication, negation.

\DESCRIBE
When applied to a theorem {A |- ~t}, the inference rule {NOT_ELIM} returns the
theorem {A |- t ==> F}.
{
      A |- ~t
   --------------  NOT_ELIM
    A |- t ==> F
}
\FAILURE
Fails unless the theorem has a negated conclusion.

\SEEALSO
IMP_ELIM, NOT_INTRO.

\ENDDOC