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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.
\EXAMPLE
{
# let th = REWRITE_RULE[ARITH] (ASSUME `1 = 0`);;
val th : thm = 1 = 0 |- F
# CONTR `Russell:Person = Pope` th;;
val it : thm = 1 = 0 |- Russell = Pope
}
\SEEALSO
CCONTR, CONTR_TAC, NOT_ELIM.
\ENDDOC
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