listLib.LENGTH

STRUCTURE

SYNOPSIS

Computes by inference the length of an object-language list.

DESCRIPTION

For any object language list of the form “[x1;x2;...;xn]”, where x1, x2, ..., xn are arbitrary terms of the same type, the result of evaluating

   LENGTH_CONV “LENGTH [x1;x2;...;xn]”

is the theorem

   |- LENGTH [x1;x2;...;xn] = n

where n is the numeral constant that denotes the length of the list.

FAILURE

LENGTH_CONV tm fails if tm is not of the form “LENGTH [x1;x2;...;xn]” or “LENGTH []”.