CCONTR : (term -> thm -> thm)

SYNOPSIS
Implements the classical contradiction rule.

DESCRIBE
When applied to a term t and a theorem A |- F, the inference rule CCONTR returns the theorem A - {~t} |- t.
       A |- F
   ---------------  CCONTR t
    A - {~t} |- t

FAILURE
Fails unless the term has type bool and the theorem has F as its conclusion.

COMMENTS
The usual use will be when ~t exists in the assumption list; in this case, CCONTR corresponds to the classical contradiction rule: if ~t leads to a contradiction, then t must be true.

SEEALSO  CONTR,   CONTRAPOS,   CONTR_TAC,   NOT_ELIM

HOL  Kananaskis 0