That one strikes me as odd, also. Perhaps it's to prevent people from calculating center of mass?
But why would anyone want to prevent that type of calculation? -- Raul On Sat, Apr 11, 2015 at 5:41 PM, Devon McCormick <[email protected]> wrote: > Hi Bob - > > this sounds interesting but why would Meter*Gram be forbidden? If I'm > calculating Newtons, I want Kg * M/s^2, don't I? > > Regards, > > Devon > > On Sat, Apr 11, 2015 at 4:37 PM, Robert Bernecky <[email protected]> > wrote: > >> In the recent discussion on typing in J, I cited the Gimley Glider >> and the Mars Climate Orbiter as events in which confusion over >> units of measure caused expensive problems and near-disaster >> (disaster in the case of the MCO). >> >> This morning, I was reading the SIGPLAN Haskell Symposium '14 >> Proceedings, and found this article: >> >> http://www.cis.upenn.edu/~eir/papers/2014/units/units.pdf >> >> By way of introduction, the paper cites the same two events, and also >> cites (bottom of page 1) a paper that gives more of the same. >> The paper is worth reading, IMO, because the authors create >> DIMENSIONs: mass, length, density, volume, etc., that are >> independent of units (kilogram, furlong, fortnight). >> They also introduce two kinds of combinators (adverbs) that >> can modify the dimensions, e.g,: >> >> type Velocity = Length: / Time >> type Kilogram = Kilo :@ Gram NB. Kilo is prefix, not unit >> >> This lets them do things such as multiplying Kilograms times Gram >> (and getting the right answer) , while forbidding Meter * Gram. >> >> I think these folks have some good ideas that could be exploited >> in J and APL to everyone's benefit. >> >> Bob >> >> -- >> Robert Bernecky >> Snake Island Research Inc >> 18 Fifth Street >> Ward's Island >> Toronto, Ontario M5J 2B9 >> >> [email protected] >> tel: +1 416 203 0854 >> >> ---------------------------------------------------------------------- >> For information about J forums see http://www.jsoftware.com/forums.htm >> > > > > -- > Devon McCormick, CFA > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
