File: CONTR.doc

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\DOC CONTR

\TYPE {CONTR : (term -> thm -> thm)}

\SYNOPSIS
Implements the intuitionistic contradiction rule.

\KEYWORDS
rule, contradiction.

\DESCRIBE
When applied to a term {t} and a theorem {A |- F}, the inference rule {CONTR}
returns the theorem {A |- t}.
{
    A |- F
   --------  CONTR "t"
    A |- t
}
\FAILURE
Fails unless the term has type {bool} and the theorem has {F} as its
conclusion.

\SEEALSO
CCONTR, CONTRAPOS, CONTR_TAC, NOT_ELIM.

\ENDDOC