ELL_CONV
listLib.ELL_CONV : conv
Computes by inference the result of indexing an element of a list from the tail end.
For any object language list of the form “[xn-1;...;xk;...x0]” , the
result of evaluating
ELL_CONV “ELL k [xn-1;...;xk;...;x0]”
is the theorem
|- ELL k [xn-1;...;xk;...;x0] = xk
where k must not be greater then the length of the list. Note that
ELL indexes the list elements from the tail end.
Failure
ELL_CONV tm fails if tm is not of the form described above, or k
is not less than the length of the list.