File: mk_iff.doc

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\DOC mk_iff

\TYPE {mk_iff : term * term -> term}

\SYNOPSIS
Constructs a logical equivalence (Boolean equation).

\DESCRIBE
{mk_iff(`t1`,`t2`)} returns {`t1 <=> t2`}. 

\FAILURE
Fails with unless {t1} and {t2} both have Boolean type.

\EXAMPLE
{
  # mk_iff(`x = 1`,`1 = x`);;
  val it : term = `x = 1 <=> 1 = x`
}

\COMMENTS
Simply {mk_eq} has the same effect on successful calls. However {mk_iff} is 
slightly more efficient, and will fail if the terms do not have Boolean type.

\SEEALSO
dest_iff, is_iff,mk_eq.

\ENDDOC