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SOME_EL_CONV                                                 (listLib)
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SOME_EL_CONV : conv -> conv

SYNOPSIS
Computes by inference the result of applying a predicate to the elements of a
list.

KEYWORDS
conversion, list.

DESCRIBE
{SOME_EL_CONV} takes a conversion {conv} and a term {tm} of the following form:

   SOME_EL P [x0;...xn]

It returns the theorem

   |- SOME_EL P [x0;...xn] = F

if for every {xi} occurred in the list, {conv “P 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

   |- SOME_EL P [x0;...xn] = T


FAILURE
{SOME_EL_CONV conv tm} fails if {tm} is not of the form described above, or
failure occurs when evaluating {conv “P xi”} for some {xi}.

EXAMPLE
Evaluating

   SOME_EL_CONV bool_EQ_CONV “SOME_EL ($= T) [T;F;T]”;

returns the following theorem:

   |- SOME_EL($= T)[T;F;T] = T

In general, if the predicate {P} is an explicit lambda abstraction
{(\x. P x)}, the conversion should be in the form

   (BETA_CONV THENC conv')


SEEALSO
listLib.ALL_EL_CONV, listLib.IS_EL_CONV, listLib.FOLDL_CONV,
listLib.FOLDR_CONV, listLib.list_FOLD_CONV.

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