Improvements to typecasting in %^{+ls

% - %<int><seq> = <seq>[::<int>]
^ - ^<seq><int> = cartesian product of <seq. with n elements.
{ - {<int> = {<int>}
+ - appends onto front or end of list if add not list to list or vice versa.
l - Takes log base 2 of ints, floats.
s - can sum tuples and lists.
Changes to y,u. y is infite range, powerset. u akes default value.
Updated y.