AND_EL_CONV : conv
STRUCTURE
listLib
SYNOPSIS
Computes by inference the result of taking the conjunction of the elements of a boolean list.
DESCRIPTION
For any object language list of the form --`[x1;x2;...;xn]`--, where x1, x2, ..., xn are boolean expressions, the result of evaluating 
   AND_EL_CONV (--`AND_EL [x1;x2;...;xn]`--)
is the theorem 
   |- AND_EL [x1;x2;...;xn] = b
where b is either the boolean constant that denotes the conjunction of the elements of the list, or a conjunction of those xi that are not boolean constants.
EXAMPLE
- AND_EL_CONV (--`AND_EL [T;F;F;T]`--);
|- AND_EL [T;F;F;T] = F

- AND_EL_CONV (--`AND_EL [T;T;T]`--);
|- AND_EL [T;T;T] = T

- AND_EL_CONV (--`AND_EL [T;x;y]`--);
|- AND_EL [T; x; y] = x /\ y

- AND_EL_CONV (--`AND_EL [x;F;y]`--);
|- AND_EL [x; F; y] = F

FAILURE
AND_EL_CONV tm fails if tm is not of the form described above.
HOL  Kananaskis-10