SELECT - select one value from a list.

SELect(I1,X0,X1,...)

returns the value of one of its arguments. I1 must be an integer; other arguments can have any type. If I1 is 0, SELect returns X0, if I1 is 1, SELect returns X1, and so on. If there is no argument corresponding to the value of I1, SELect returns the last argument in the list.