Raul, thank you for the detailed explanation and alternate code. I was
using this as an opportunity to learn gerunds. As a bonus, from your reply
I was able to learn more about custom adverbs and conjunctions.
I agree that the adverb approach makes more sense then a verb for every
column and operator. I can envision wanting to do > and < and other
operations, which would make sense as adverb just eq. I was also glad to
find out that I could mimic what Martin had in his videos too with FName_eq
This works well:
(<'John') FName eq (<'Acme') Company eq data(<'John') FName eq (<'Acme')
Company eq data
In terms of sel, I had to modify yours slightly to make it work: I'm
including it here for completeness
NB. Raul's first version
sel2=:2 :0
(v u) # ]
)
('`',;:inv cols,L:0 '_eq2')=: 3 :'{. = sel2 (y`:6)`'''''"0 cols
(<'John') FName_eq2 data
|length error: FName
| (<'John') FName_eq2 data
NB. Pascal's version
sel3=:2 : '(u v ]) # ]'
('`',;:inv cols,L:0 '_eq3')=: 3 :'{. = sel3 (y`:6)`'''''"0 cols
(<'John') FName_eq3 data
|length error: FName_eq3
| (<'John') FName_eq3 data
NB. Raul's second version
sel=:2 :0
v@u # ]
)
('`',;:inv cols,L:0 '_eq')=: 3 :'{. = sel (y`:6)`'''''"0 cols
(<'John') FName_eq data
|length error: FName_eq
| (<'John') FName_eq data
NB. Joe's final version
sel4=:2 :0
(u v) # ]
)
('`',;:inv cols,L:0 '_eq4')=: 3 :'{. = sel4 (y`:6)`'''''"0 cols
(<'John') FName_eq4 data
+----+-----+--+----+
|John|Smith|31|Acme|
+----+-----+--+----+
It's easy to see the differences:
FName_eq NB. v@u # ]
FName@= # ]
FName_eq2 NB. (v u) # ]
(FName =) # ]
FName_eq3 NB. (u v ]) # ]
(= FName ]) # ]
FName_eq4 NB. (u v) # ] --> correct
(= FName) # ]
Where FName_eq4 is the only one I could get to work.
Pascal -- regarding the eval and evalassign. Neat tricks. I will keep that
at hand too
I feel much more comfortable with gerunds, adverbs and conjunctions...
Thanks!
On Fri, Apr 25, 2014 at 11:57 PM, Raul Miller <rauldmil...@gmail.com> wrote:
> That won't work.
>
> Actually, my code had a bug in it also, for what I think is the intended
> use pattern. It's also the case (u v ]) # ] is not equivalent to (v u) # ]
> but since (v u) # ] does not do the right job, let's skip on to what I
> think I should have defined:
>
> sel=:2 :0
> v@u # ]
> )
>
> Here's a test case:
>
> prime=: = ]&.(p:inv)
>
> prime 2 3 4
>
> 1 1 0
>
> penultimate=: _2&{"1
>
> prime sel penultimate i. 5 5
>
> 0 1 2 3 4
>
> 10 11 12 13 14
>
> 20 21 22 23 24
>
>
> (This example gets the rows of i.5 5 where the value in the second to last
> column is prime.)
>
>
> Thanks,
>
>
> --
>
> Raul
>
>
>
>
>
> On Fri, Apr 25, 2014 at 11:43 PM, 'Pascal Jasmin' via Programming <
> programm...@jsoftware.com> wrote:
>
> > good post, Raul thank you.
> >
> > I just want to rant on a pet peave about hooks.
> >
> > sel=:2 :0
> > (v u) # ]
> > )
> >
> > is better defined as:
> >
> > sel=:2 : '(u v ]) # ]'
> >
> > for one, its needed to allow u to be a noun.
> >
> > The point relating to my pet peave about hooks, is that it also allows u
> > to be dyadic. Not that I have a great use case for it, in this example.
> >
> > 1 2: sel < i.5
> > 3 4
> >
> >
> > ----- Original Message -----
> > From: Raul Miller <rauldmil...@gmail.com>
> > To: Programming forum <programm...@jsoftware.com>
> > Cc:
> > Sent: Friday, April 25, 2014 9:35:02 PM
> > Subject: Re: [Jprogramming] J in 5 minutes
> >
> > Ah, I see...
> >
> > I'd like to draw your attention to something in my code here:
> >
> > colN=:3 : 0
> > {.y&{"1`''
> > )
> > '`FName LName Age Company'=: colN"0 i.4
> >
> > Notice that the expression on the far right is: colN"0 i. 4
> >
> > That ("0) means that colN is running independently for each value in i.4
> >
> > Also, I already knew what my column names were, so I did not bother
> > abstracting them.
> >
> > Now it looks like you want to have the name list as an argument and build
> > up operations based on those names. Personally, I tend to shy away from
> > abstractions unless I feel they will help (J gives a lot of abstraction
> > already). Still, let's look at some alternatives for the way you
> currently
> > have things expressed:
> >
> > cols=: 'FName';'LName';'Age';'Company'
> > vars=:('`',(, > (],&'_eq ') each cols))
> > verbs=:". }. ,> ('`',[) each ('((= ' , ') # ])' ,~ ]) each cols
> >
> > Here's how I might express those two first two lines:
> > cols=: ;:'FName LName Age Company'
> > vars=: '`',;:inv cols,L:0 '_eq'
> >
> > But verbs is a bit different. I'd be tempted to not bother with names of
> > the form FName_eq and instead use an adverb:
> > eq=:1 :0
> > (= u) # ]
> > )
> >
> > Then, instead of FName_eq, I would use FName eq
> >
> > Or, (contradicting my earlier statement about avoiding abstraction - but
> > what I really meant was that I like simple, direct abstractions, but
> mostly
> > it's hard for me to describe "how I think" in a meaningful fashion):
> >
> > sel=:2 :0
> > (v u) # ]
> > )
> >
> > Now, instead of FName_eq or FName eq, I would use = sel FName
> >
> > But let's say that I wanted to define those verbs. First, notice
> something:
> >
> > cols-:FName`LName`Age`Company
> > 1
> >
> > A boxed list of names of verbs is equivalent to a gerund listing those
> > verbs by name. And that relates back to what colN was doing (forming a
> > gerund length one and taking the first and only box from that list). I
> can
> > perform a similar trick here:
> >
> > ('`',;:inv cols,L:0 '_eq')=: 3 :'{. = sel (y`:6)`'''''"0 cols
> >
> > Does this make sense?
> >
> > Thanks,
> >
> > --
> > Raul
> >
> >
> >
> > On Fri, Apr 25, 2014 at 9:02 PM, Joe Bogner <joebog...@gmail.com> wrote:
> >
> > > On Fri, Apr 25, 2014 at 7:44 PM, Raul Miller <rauldmil...@gmail.com>
> > > wrote:
> > >
> > > > On Fri, Apr 25, 2014 at 5:31 PM, Joe Bogner <joebog...@gmail.com>
> > wrote:
> > > >
> > > > > So I can generate a string and evaluate it, but is there a better
> way
> > > > than
> > > > > evaluating the string?
> > > > >
> > > >
> > > > Here are some options:
> > > >
> > > > ". (or do - the advantage of do being that it's a name so you can
> > specify
> > > > which locale to use).
> > > >
> > > >
> > > My goal is to define a list of helper verbs for each column in the
> table.
> > >
> > > I used ". in my last version. It was somewhat cryptic, so here it is
> > again
> > > with more details:
> > >
> > > cols=: 'FName';'LName';'Age';'Company'
> > >
> > > ] vars=:('`',(, > (],&'_eq ') each cols))
> > >
> > > `FName_eq LName_eq Age_eq Company_eq
> > >
> > >
> > >
> > > ] verbs=:". }. ,> ('`',[) each ('((= ' , ') # ])' ,~ ]) each cols
> > >
> > >
> > >
> > >
> > >
> >
> ┌───────────────────────┬───────────────────────┬─────────────────────┬─────────────────────────┐
> > >
> > >
> > >
> >
> │┌─┬───────────────────┐│┌─┬───────────────────┐│┌─┬─────────────────┐│┌─┬─────────────────────┐│
> > >
> > >
> > >
> >
> ││3│┌─────────────┬─┬─┐│││3│┌─────────────┬─┬─┐│││3│┌───────────┬─┬─┐│││3│┌───────────────┬─┬─┐││
> > >
> > > ││ ││┌─┬─────────┐│#│]││││ ││┌─┬─────────┐│#│]││││
> ││┌─┬───────┐│#│]││││
> > > ││┌─┬───────────┐│#│]│││
> > >
> > > ││ │││2│┌─┬─────┐││ │ ││││ │││2│┌─┬─────┐││ │ ││││ │││2│┌─┬───┐││ │
> ││││
> > > │││2│┌─┬───────┐││ │ │││
> > >
> > > ││ │││ ││=│FName│││ │ ││││ │││ ││=│LName│││ │ ││││ │││ ││=│Age│││ │
> ││││
> > > │││ ││=│Company│││ │ │││
> > >
> > > ││ │││ │└─┴─────┘││ │ ││││ │││ │└─┴─────┘││ │ ││││ │││ │└─┴───┘││ │
> ││││
> > > │││ │└─┴───────┘││ │ │││
> > >
> > > ││ ││└─┴─────────┘│ │ ││││ ││└─┴─────────┘│ │ ││││ ││└─┴───────┘│ │
> ││││
> > > ││└─┴───────────┘│ │ │││
> > >
> > > ││ │└─────────────┴─┴─┘│││ │└─────────────┴─┴─┘│││
> │└───────────┴─┴─┘│││
> > > │└───────────────┴─┴─┘││
> > >
> > >
> > >
> >
> │└─┴───────────────────┘│└─┴───────────────────┘│└─┴─────────────────┘│└─┴─────────────────────┘│
> > >
> > >
> > >
> > >
> >
> └───────────────────────┴───────────────────────┴─────────────────────┴─────────────────────────┘
> > >
> > >
> > >
> > > (I don't know how to paste this better)
> > >
> > >
> > > (vars)=:verbs
> > >
> > >
> > > FName_eq
> > >
> > >
> > > (= FName) # ]
> > >
> > >
> > >
> > > I can now execute statements like this: (<'John') FName_eq (<'Acme')
> > > Company_eq data
> > >
> > >
> > > This works fine, but I wanted to get input on it vs other other
> > approaches.
> > >
> > >
> > >
> > > More specifically, you used this:
> > >
> > >
> > > colN=:3 : 0
> > > {.y&{"1`''
> > > )
> > > '`FName LName Age Company'=: colN"0 i.4
> > >
> > >
> > > I don't quite understand how it works and I was wondering if it's
> better
> > > than using Do. I don't know how to have a verb return a train of verbs
> > for
> > > a gerund. I may be using the wrong terminology.
> > >
> > > [colN"0 i.1
> > >
> > > ┌─────────────────────────┐
> > >
> > > │┌─┬─────────────────────┐│
> > >
> > > ││"│┌─────────────┬─────┐││
> > >
> > > ││ ││┌─┬─────────┐│┌─┬─┐│││
> > >
> > > ││ │││&│┌─────┬─┐│││0│1││││
> > >
> > > ││ │││ ││┌─┬─┐│{│││└─┴─┘│││
> > >
> > > ││ │││ │││0│0││ │││ │││
> > >
> > > ││ │││ ││└─┴─┘│ │││ │││
> > >
> > > ││ │││ │└─────┴─┘││ │││
> > >
> > > ││ ││└─┴─────────┘│ │││
> > >
> > > ││ │└─────────────┴─────┘││
> > >
> > > │└─┴─────────────────────┘│
> > >
> > > └─────────────────────────┘
> > >
> > >
> > >
> > > I can come reasonable close, but not the final mile. No big deal if Do.
> > is
> > > good enough, since it works
> > >
> > >
> > > '`FName_eq LName_eq' =: (3 : '=&y` '''' ' ) each 'FName';'LName'
> > >
> > >
> > > FName_eq
> > >
> > >
> > > =&'FName'
> > >
> > >
> > >
> > > I would ideally like something like this (I think), assuming this
> better
> > > than do:
> > >
> > >
> > > '`FName_eq LName_eq' =:(3 :'(= y) #]` '''' ')each'FName';'LName'
> > >
> > > |length error
> > >
> > > | (=y) #]`''
> > >
> > >
> > > But again, I don't really understand what it's doing with the verb
> > > returning a strange form that somewhat appears to be a gerund
> > > ----------------------------------------------------------------------
> > > For information about J forums see http://www.jsoftware.com/forums.htm
> >
> > >
> > ----------------------------------------------------------------------
> > For information about J forums see http://www.jsoftware.com/forums.htm
> > ----------------------------------------------------------------------
> > For information about J forums see http://www.jsoftware.com/forums.htm
> >
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
