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\DOC IS_EL_CONV
\TYPE {IS_EL_CONV : conv -> conv}
\SYNOPSIS
Computes by inference the result of testing whether a list contains acertain element.
\KEYWORDS
conversion, list.
\DESCRIBE
{IS_EL_CONV} takes a conversion {conv} and a term {tm} in the following form:
{
IS_EL x [x0;...xn]
}
\noindent It returns the theorem
{
|- IS_EL x [x0;...xn] = F
}
\noindent if for every {xi} occurred in the list, {conv "x = xi"}
returns a theorem {|- P xi = F}, otherwise, if for at least one {xi},
evaluating {conv "P xi"} returns the theorem {|- P xi = T}, then it
returns the theorem
{
|- IS_EL P [x0;...xn] = T
}
\FAILURE
{IS_EL_CONV conv tm} fails if {tm} is not of the form described above, or
failure occurs when evaluating {conv "x = xi"} for some {xi}.
\EXAMPLE
Evaluating
{
IS_EL_CONV bool_EQ_CONV "IS_EL T [T;F;T]";;
}
\noindent returns the following theorem:
{
|- IS_EL($= T)[F;F] = F
}
\SEEALSO
SOME_EL_CONV, ALL_EL_CONV, FOLDL_CONV, FOLDR_CONV, list_FOLD_CONV.
\ENDDOC
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