Pascal, thank you for your feedback and suggestion.
Raul, your implementation is what I was hoping for. It is concise and
readable. I like that each match type requires only a single line --
less ceremony and more to the point. The return on first match is nice
too.
I particularly liked the multi-statement if.
getIf=: 4 :0
if. data=: ".x
n=: #y
idx=: (n{."1 data) i. y
3 < idx getCtCol data
do. x; idx getValCol data end.
)
I'm used to thinking of if statements as purely testing conditionals.
I had to look it up to understand it better:
http://www.jsoftware.com/help/dictionary/ctrl.htm
"The last sentence executed in a T block is tested for a non-zero
value in its leading atom, and determines the block to be executed
next"
I probably would have written it like this without thinking of putting
the assignments in the if.
getIf=: 4 :0
data=: ".x
n=: #y
idx=: (n{."1 data) i. y
if. 3 < idx getCtCol data
do. x; idx getValCol data return. end.
'' NB. blank return by default
)
or
getIf=: 4 :0
data=: ".x
n=: #y
idx=: (n{."1 data) i. y
ret=:''
if. 3 < idx getCtCol data
do. ret=: x; idx getValCol data end.
)
Making it part of the if. is cleaner
Thanks,
Joe
On Sat, Oct 3, 2015 at 2:49 PM, Raul Miller <[email protected]> wrote:
> Oh, DUH!
>
> You are right, the implementation is right, I am wrong.
>
> Here's a fixed version of my implementation:
>
> getIf=: 4 :0
> if. data=: ".x
> n=: #y
> idx=: (n{."1 data) i. y
> 3 < idx getCtCol data
> do. x; idx getValCol data end.
> )
>
> getVal =: 3 : 0
> NB. search for the full key in city_sport (e.g. hat;chicago;baseball
> if. #ret=: 'city_sport' getIf y do. ret return. end.
> NB. search for city
> if. #ret=: 'city' getIf 2 {. y do. ret return. end.
> NB. search for sport, meaning we need the 1st and 3rd value from the key
> if. #ret=: 'sport' getIf 0 2 { y do. ret return. end.
> NB. search for item overall
> if. #ret=: 'item' getIf 1 {. y do. ret return. end.
> ''
> )
>
> Thanks!
>
> --
> Raul
>
>
> On Sat, Oct 3, 2015 at 2:33 PM, 'Pascal Jasmin' via Programming
> <[email protected]> wrote:
>> 3 : 'if. i.0 do. 1 else. 0 end.' 31
>> didn't know this was a bug, but something strange for sure.
>> From: Raul Miller <[email protected]>
>> To: Programming forum <[email protected]>
>> Sent: Saturday, October 3, 2015 2:10 PM
>> Subject: Re: [Jprogramming] comparing languages - input to show J's
>> strength on a lookup/match function
>>
>> Unfortunately, my first attempt to rewrite your code seems to trigger
>> an interpreter bug.
>>
>> For reference, here's my attempt:
>>
>> getIf=: 4 :0
>> if. data=: ".x
>> n=: #y
>> idx=: (n{."1 data) i. y
>> 3 < idx getCtCol data
>> do. x; idx getValCol data end.
>> )
>>
>> getVal =: 3 : 0
>> NB. search for the full key in city_sport (e.g. hat;chicago;baseball
>> if. ret=: 'city_sport' getIf y do. ret return. end.
>> NB. search for city
>> if. ret=: 'city' getIf 2 {. y do. ret return. end.
>> NB. search for sport, meaning we need the 1st and 3rd value from the key
>> if. ret=: 'sport' getIf 0 2 { y do. ret return. end.
>> NB. search for item overall
>> if. ret=: 'item' getIf 0 { y do. ret return. end.
>> ''
>> )
>>
>> What seems to happen is that only the city_sport table gets tested,
>> even with empty ret values from that lookup.
>>
>> This violates the dictionary definition for if.
>>
>> I guess this means that I'm going to need to go in and find why this
>> is happening (unless someone else gets to it before me).
>>
>> Thanks,
>>
>> --
>> Raul
>>
>>
>> On Sat, Oct 3, 2015 at 8:45 AM, Joe Bogner <[email protected]> wrote:
>>> I'm working on an app that needs a function to return a value based upon
>>> matching to 4 different sources and returns the most specific match that
>>> meets a quality threshold.
>>>
>>> Here is an example:
>>>
>>> The last column of every table (e.g. city_sport) indicates the quality
>>> threshold and the column before that is the value I'd like if the quality
>>> threshold is above 3
>>>
>>> The logic in words:
>>>
>>> Search city_sport
>>> if not found or quality not sufficient, search city
>>> if not found or quality not sufficient search sport
>>> if not found or quality not sufficient search item
>>>
>>> The logic works. I wrote it quickly in J using my natural imperative
>>> mindset. I then was able to very quickly translate it into C# (probably
>>> demonstrating how imperative my mindset was)
>>>
>>> J version: https://gist.github.com/joebo/381552e6ad106391e128
>>> C# version: https://gist.github.com/joebo/a0ff7eb57ee15ea96c61
>>>
>>> I'm looking for input on how to rewrite getVal to show improved
>>> maintenance, conciseness over the C# version (subjective, I know)
>>>
>>> Some half-baked thoughts:
>>>
>>> 1. Instead of using the if., at each step build up all the possible results
>>> and find the result in the final step
>>>
>>> Note: this will be searching a table of 180,000 rows so performance may
>>> matter. The current J version doesn't short circuit, but it could fairly
>>> easily
>>>
>>> 2. Some trick with agenda
>>>
>>>
>>> Thanks for any input
>>>
>>> Code below:
>>>
>>> city_sport=: ' ' cut every <;._2 (0 : 0)
>>> hat chicago baseball 1 5
>>> hat chicago football 2 5
>>> hat atlanta baseball 3 2
>>> hat orlando football 3 3
>>> glove orlando baseball 3 3
>>> )
>>>
>>> city=: ' ' cut every <;._2 (0 : 0)
>>> hat chicago 1 5
>>> hat atlanta 3 2
>>> hat orlando 3 3
>>> glove orlando 3 3
>>> )
>>>
>>> sport=: ' ' cut every <;._2 (0 : 0)
>>> hat baseball 1 5
>>> hat football 3 2
>>> jersey soccer 3 4
>>> )
>>>
>>> item=: ' ' cut every <;._2 (0 : 0)
>>> hat 1 5
>>> jersey 2 4
>>> )
>>>
>>> NB. gets the count which is always the last column
>>> getCtCol =: ([: ". [: > _1 { {) :: 0:
>>>
>>> NB. gets the value which is always 2nd to last column
>>> getValCol =: ([: ". [: > _2 { {) :: 0:
>>>
>>> getVal =: 3 : 0
>>> NB. search for the full key in city_sport (e.g. hat;chicago;baseball
>>> idx =: 0 { (3{."1 city_sport) i. (,: y)
>>> ret=:''
>>> if. (idx getCtCol city_sport) > 3 do.
>>> ret =: 'city_sport';(idx getValCol city_sport)
>>> end.
>>> NB. search for city
>>> idx =: 0 { (2{."1 city) i. (,: 2{."1 y)
>>> if. (0 = (#ret)) *. (idx getCtCol city) > 3 do.
>>> ret =: 'city';(idx getValCol city)
>>> end.
>>> NB. search for sport, meaning we need the 1st and 3rd value from the key
>>> idx =: 0 { (2{."1 sport) i. (,: 0 2 { y)
>>> if. (0 = (#ret)) *. (idx getCtCol sport) > 3 do.
>>> ret =: 'sport';(idx getValCol sport)
>>> end.
>>> NB. search for item overall
>>> idx =: 0 { (1{."1 item) i. (,: 0 { y)
>>> if. (0 = (#ret)) *. (idx getCtCol item) > 3 do.
>>> ret =: 'item';(idx getValCol item)
>>> end.
>>> ret
>>> )
>>>
>>> smoutput getVal 'hat';'chicago';'baseball'
>>> smoutput getVal 'hat';'chicago';'hockey'
>>> smoutput getVal 'jersey';'chicago';'soccer'
>>> smoutput getVal 'jersey';'chicago';'badmitton'
>>>
>>> NB. not enough hats in the city/sport match or city match
>>> smoutput getVal 'hat';'atlanta';'baseball'
>>>
>>>
>>> Outputs:
>>>
>>> smoutput getVal 'hat';'chicago';'baseball'
>>>
>>> ┌──────────┬─┐
>>>
>>> │city_sport│1│
>>>
>>> └──────────┴─┘
>>>
>>> smoutput getVal 'hat';'chicago';'hockey'
>>>
>>> ┌────┬─┐
>>>
>>> │city│1│
>>>
>>> └────┴─┘
>>>
>>> smoutput getVal 'jersey';'chicago';'soccer'
>>>
>>> ┌─────┬─┐
>>>
>>> │sport│3│
>>>
>>> └─────┴─┘
>>>
>>> smoutput getVal 'jersey';'chicago';'badmitton'
>>>
>>> ┌────┬─┐
>>>
>>> │item│2│
>>>
>>> └────┴─┘
>>> ----------------------------------------------------------------------
>>> 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
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