Hi Lindsay, On Mon, Feb 27, 2017 at 06:28:15AM -0600, Erik Gustafson wrote: > With '*/', I like to think of it like this: for multiplication, the scale > factor is last, e.g. > > (*/ X Y Scl) > > For division, the scale factor comes first, e.g. > > (*/ Scl X Y)
Exactly. The reason is simply that if you multiply two scaled integers, you have to divide by the scale factor afterwards. For example, assume your integers denote centimeters. You set *Scl to 2, so that 100 cm = 1.0 m Now, one square meter is 1.0 m * 1.0 m = 100 cm * 100 cm = 1.0 m^2 = 10000 cm^2 As we want the result not in cm but in meters, we must divide by 100. Example: :(scl 2) -> 2 : (*/ 3.0 4.0 1.0) # This is equal to (*/ 300 400 100) -> 1200 : (round @) -> "12.00" For division you need the opposite, multiply with 100 instead of dividing. So you first multiply thi dividend by the scale factor before you divide: (*/ 12.0 1.0 3.0) # this is 12.0 / 3.0 If you multiply more than two numbers, you have to use the corresponding scale factor: : (*/ 3.0 4.0 5.0 `(* 1.0 1.0)) # 3.0 * 4.0 * 5.0 -> 6000 : (round @) -> "60.00" ♪♫ Alex -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
