[Jprogramming] Passing class member gerund to verb in another locale

Fri Sep 1 12:44:34 UTC 2017

Hi Pascal. Thanks for the response. You are correct in this case. Not to move the goal posts, but 
 funcB_B_ geomean_A_`'' ;

will not work if geoMean is redefined to be

geoMean=: 3 : 0
NB. same as before, but add d.
 d+(#%:(*/)) y
)

The variable d was created in myA's create verb. This is not visible from _A_ locale.

I will repost the entire (modified) source below. Note that getAvg__myA calls funB_B_ with gerund geoMean__myA. 

coclass 'A'

create=: 3 : 0
d=:y
)

geoMean=: 3 : 0

 d+(#%:(*/)) y
)

myVerb=: 3 : 0
 ((geoMean )  ; (+/%#)) y
)

getAvg=: 3 : 0
data=.y
funcB_B_ (myVerb_A_ `''); data
)

cocurrent 'B'

NB. accepts the object ref as param.
NB. helper verb, for special case of
NB. classes with a member verb called myVerb.
funcB2=: 3 : 0
'obj data'=: y

verb=. 3 : ' myVerb__obj y'
funcB ((verb f.) `'');data
)

NB. More general verb, accepts any verb
NB. (assuming verb is callable from this locale)
funcB=: 3 : 0
'vrb data' =: y
f=: vrb `:6
f data
)

 myA=: 1 conew 'A'
geoMean__myA 1 2 3   NB. no problem here
   getAvg__myA 1 2 3   NB. error here

--------------------------------------------
On Fri, 9/1/17, 'Pascal Jasmin' via Programming <programming at jsoftware.com> wrote:

 Subject: Re: [Jprogramming] Passing class member gerund to verb in another locale
 To: "programming at jsoftware.com" <programming at jsoftware.com>
 Date: Friday, September 1, 2017, 8:19 PM

 funcB_B_ geomean_A_`'' ;
 data
 do not use f. inside funcB.  f. will
 lose locale info

 From: 'Jon Hough' via Programming <programming at jsoftware.com>
  To: programming at jsoftware.com

  Sent: Friday, September 1, 2017 1:09 AM
  Subject: Re: [Jprogramming] Passing class
 member gerund to verb in another locale

 I forgot to add a definition of funcB 

 cocurrent 'B'

 funcB=: 3 : 0
 'vrb data' =: y
 f=: vrb
 `: 6  NB. vrb is the gerund
 f data  NB.
 call f. This creates the error.
 )

 --------------------------------------------
 On Fri, 9/1/17, 'Jon Hough' via
 Programming <programming at jsoftware.com>
 wrote:

  Subject:
 [Jprogramming] Passing class member gerund to verb in
 another locale
  To: "Programming
 Forum" <programming at jsoftware.com>
  Date: Friday, September 1, 2017, 2:03 PM

  My problem is,  I have a
 class 'A' say.
  and I have a locale
 'B'.

  A contains
 several verbs. I would like
  to pass a verb
 (or gerunds of the verbs), let's call it
  myVerb, to some verb in B. However, this
 creates a problem,
  as
  when
 the B verb tries to call myVerb it
  cannot
 find it, being in a different locale. i.e. I get a
  value error. I attempted to use fix (f.) to
 get myVerb
  explicitly, but this only
  works if myVerb does not contain any
  other verbs from A.

  This is the contrived example, that is
  essentially the same as my real problem, but
 stripped of
  superfluous things:

  NB. A is some class with
 several
  verbs.
  coclass
 'A'

  create=: 3 : 0
  d=:y 
  )

  NB. some
 verb in A
  geoMean=: 3 : 0
   (#%:(*/)) y
  )

  NB. I want
 to pass this to another verb
  in another
 locale.
  NB. Note that it calls geoMean.
  myVerb =: 3 : 0
   ((geoMean
 f.)  ; (+/%#)) y
  )

  NB. calling a verb in B
  getAvg=: 3 : 0
  data=.y
  funcB_B_ ( myVerb f. `''); data
  )

  NB.
 create my instance of A
  myA =: 0 conew
 'A'
  NB. call myVerb. No problem
 here!
  myVerb__myA 1 2 3

 NB. pass myVerb to funcB_B_
  getAvg__myA 1 2
 3
  NB. this gives an error

 |value error: geoMean
  |   ((geoMean   

  f.);(+/%#))y

 Solutions:
  (1) One solution is to make
 funcB_B_ a
  conjunction / adverb. But in
 reality, I want to send several
  verbs to
 funcB together. 
  (2) Another solution is to
 send the
  instance reference of A to funcB
 (i.e. just send the whole
  of myA to funcB).
 But I would prefer not to send the whole

 object, as it then makes B less flexible, because I may
 want
  to call funcB_B_ without the need for
 a class instance, just
  a standalone
 verb.
  (3) Another solution is to not call
 any
  other verbs of myA inside myVerb__myA.
 This is not a
  realistic solution as A could
 be quite complicated.

  Is there a better way?

  Just to explain my motivation, I am
  trying to replicate the functionality most
 languages that
  have first-class functions
 possess - to pass arbitrary
  function(s)
 to
  other functions and call them.
  e.g. in  Python

  # myVerb is a Python function, and
  could be a member method of some class.
 someData is just
  some data

 def funcB (myVerb, someData):
      return
 myVerb(someData,
  someOtherData)

  Obviously J doesn't have
 first class
  functions in this sense, but
 with gerunds, I was hoping to
  be able to
 recreate the functionality. 

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