For any object language list of the form “[x1;x2;...;xn]”, where x1,
x2, ..., xn are numeral constants, the result of evaluating
SUM_CONV “SUM [x1;x2;...;xn]”
is the theorem
|- SUM [x1;x2;...;xn] = n
where n is the numeral constant that denotes the sum of the elements of the list.