On Tue, Sep 16, 2008 at 11:23 AM, Tracy Harms <[EMAIL PROTECTED]> wrote: > deriv (f . g) x = deriv f (g x) . deriv g x > > I'm confused by the use of composition on the right-hand side, as I > expect it to involve two functions. I can't see a composition of two > functions here; in J terms, I see nouns where I expect verbs. > Guidance in correcting my misinterpretation is welcome.
In J terms, dot would be a conjunction (though you would need to rearrange that sentence so J could parse it properly): When dot's arguments are both nouns, dot produces a new noun using multiplication. (Hypothetically speaking, if neither of those nouns was rank zero, dot would probably use +/ .*). When dot's arguments are both verbs, dot produces a new verb using function composition. Note that this approach implies that the result of deriv is a noun. (However, properly speaking, I think that it should be a limit condition.) At least, that's how I would interpret that notation. (But I did not properly understand John Randall's contribution to this thread). FYI, -- Raul ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
