formal/hol/Help/BETA_TAC.doc

\DOC BETA_TAC

\TYPE {BETA_TAC : tactic}

\SYNOPSIS
Beta-reduces all the beta-redexes in the conclusion of a goal.

\KEYWORDS
tactic.

\DESCRIBE
When applied to a goal {A ?- t}, the tactic {BETA_TAC} produces a new goal
which results from beta-reducing all beta-redexes, at any depth, in {t}.
Variables are renamed where necessary to avoid free variable capture.
{
    A ?- ...((\x. s1) s2)...
   ==========================  BETA_TAC
     A ?- ...(s1[s2/x])...
}

\FAILURE
Never fails, but will have no effect if there are no beta-redexes.

\COMMENTS
Beta-reduction, and indeed, generalized beta reduction ({GEN_BETA_CONV}) are
already among the basic rewrites, so happen anyway simply on {REWRITE_TAC[]}.
But occasionally it is convenient to be able to invoke them separately.

\SEEALSO
BETA_CONV, BETA_RULE, GEN_BETA_CONV.

\ENDDOC