Even shorter:
       +&.%/ 10 20 40
5.71429

Shorthand for
    10 +&.% 20 +&.% 40
5.71429



--- Den tors 4/2/10 skrev Bo Jacoby <[email protected]>:

Fra: Bo Jacoby <[email protected]>
Emne: Re: [Jprogramming] A q for starters - composing without forking (% +/ %)
Til: "Programming forum" <[email protected]>
Dato: torsdag 4. februar 2010 08.38

   +/&.:% 10 20 40
5.71429

I was too fast. You don't even need to parenthesize (+/).

--- Den tors 4/2/10 skrev Bo Jacoby <[email protected]>:

Fra: Bo Jacoby <[email protected]>
Emne: Re: [Jprogramming] A q for starters - composing without forking (% +/ %)
Til: "Programming forum" <[email protected]>
Dato: torsdag 4. februar 2010 08.33
    %&(+/)&:% 10 20 40
5.71429
    (+/)&.:% 10 20 40
5.71429
    
Welcome Alex. The catch is to parenthesize (+/).

 --- Den tors 4/2/10 skrev Alex Gian <[email protected]>:
 
 Fra: Alex Gian <[email protected]>
 Emne: [Jprogramming] A q for starters - composing without forking (% +/ %)
Til: [email protected]
Dato: torsdag 4. februar 2010 01.36
Hi - complete newbie to J here.
Though I like what I've seen so far.

Here's my starter question:
I'd like to code the function that gives the inverse of a sum of
inverses (eg. like when calculating resistors in parallel)

It works fine if I just write it out as
     % +/ % 10 20 40            (ans 5.71429)

However, if I try to make a function of it, 
     invsuminv =. % +/ %
it becomes a fork (I guess that _does_ make sense), and just computes
the "cross-sum" of the inverses, as if I'd typed
        (% +/ %) 10 20 40
      0.2  0.15 0.125
      0.15   0.1 0.075
     0.125 0.075  0.05
 
How can I avoid this? I've tried all sorts of combinations,
using @ and & but can't seem to crack it.  Obviously something
fundamental I'm not grasping. Any help appreciated.


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