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\DOC extend_basic_convs
\TYPE {extend_basic_convs : string * (term * conv) -> unit}
\SYNOPSIS
Extend the set of default conversions used by rewriting and simplification.
\DESCRIBE
The HOL Light rewriter ({REWRITE_TAC} etc.) and simplifier ({SIMP_TAC} etc.)
have default sets of (conditional) equations and other conversions that are
applied by default, except in the {PURE_} variants. The latter are normally
term transformations that cannot be expressed as single (conditional or
unconditional) rewrite rules. A call to
{
extend_basic_convs("name",(`pat`,conv))
}
will add the conversion {conv} into the default set, using the name {name} to
refer to it and restricting it to subterms encountered that match {pat}.
\FAILURE
Never fails.
\EXAMPLE
By default, no arithmetic is done in rewriting, though rewriting with the
theorem {ARITH} gives that effect.
{
# REWRITE_CONV[] `x = 1 + 2 + 3 + 4`;;
val it : thm = |- x = 1 + 2 + 3 + 4 <=> x = 1 + 2 + 3 + 4
}
You can add {NUM_ADD_CONV} to the set of default conversions by
{
# extend_basic_convs("addition on nat",(`m + n:num`,NUM_ADD_CONV));;
val it : unit = ()
}
\noindent and now it happens by default:
{
# REWRITE_CONV[] `x = 1 + 2 + 3 + 4`;;
val it : thm = |- x = 1 + 2 + 3 + 4 <=> x = 10
}
\SEEALSO
basic_convs, extend_basic_rewrites, set_basic_convs.
\ENDDOC
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