I think {ju'u} is in the wrong selma'o. All other binary mex operands take two numbers and return a number. {ju'u} takes a naclerpoi and a number and returns a number. ze bi'esu'i bi pi'i so = (7+8)*9 ze bi'esu'i bi ju'u so = ? is it 14 (which is written 15 in base 9) or what? phma