function composition

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1

Hello:
   Is there a way to compose two function f,g without using {}?

I know (2+3-) is a composition. But I failed to define composition of (inc inc) where inc:(1+)

Thanks in advance.

2

q)inc:(1+)

q)(inc inc@)2

4

3

q)f:{[w;x;y;z]w+x+y+z}<o:p></o:p>

q)g:{2*x}<o:p></o:p>

q)h:(‘[g;f]) / The interpreter is finicky about :’<o:p></o:p>

q)h[1;2;3;4]<o:p></o:p>

20<o:p></o:p>

<o:p> </o:p>

HTH,<o:p></o:p>

<o:p> </o:p>

Kim<o:p></o:p>

<o:p> </o:p>

Von: personal-kdbplus@googlegroups.com [mailto:personal-kdbplus@googlegroups.com] Im Auftrag von Hao Deng
Gesendet: Mittwoch, 8. Oktober 2014 11:09
An: personal-kdbplus@googlegroups.com
Betreff: [personal kdb+] function composition<o:p></o:p>

<o:p> </o:p>

Hello:<o:p></o:p>

   Is there a way to compose two function f,g without using {}?<o:p></o:p>

I know (2+3-) is a composition. But I failed to define composition of (inc inc) where inc:(1+)<o:p></o:p>

<o:p> </o:p>

Thanks in advance.<o:p></o:p>

<o:p> </o:p>

–
Submitted via Google Groups

4

Thank you both Charles and Kim:
    Both usage are not documents in http://code.kx.com/wiki/Reference and anywhere I can find. 

Did I missed any documents?

5

http://code.kx.com/wiki/Reference/Apostrophe

6

Thanks Charles.
  I don’t understand the @ part. 

I understand inc@ is a curry (project) of @, 

but how does inc inc@ get parsed? Is this a special form? 

7

juxtaposition is implicit apply

q)x:abcd

q)x@2 3

cd

q)x 2 3

cd

if there’s no juxtaposition, i.e. no rhs, and you don’t want immediate evaluation, you have to explicitly insert an infix verb as the terminating token.

btw, you can pull compositions apart with value. e.g.

value(inc inc@)