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Talk:Menu: Difference between revisions
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==J implementation==
===Code removed===
because it didn't work in Beta-3: commercial/2017-04-10T17:51:14 and was flagged for improvement.
<lang j>require 'general/misc/prompt' NB. in older versions of J this was: require'misc'
showMenu =: i.@# smoutput@,&":&> ' '&,&.>
makeMsg =: 'Choose a number 0..' , ': ',~ ":@<:@#
errorMsg =: [ smoutput bind 'Please choose a valid number!'
select=: ({::~ _&".@prompt@(makeMsg [ showMenu)) :: ($:@errorMsg)</lang>
See [[Talk:Select#J_implementation|Talk page]] for explanation of code.
'''Example use:'''
<lang j> select 'fee fie'; 'huff and puff'; 'mirror mirror'; 'tick tock'</lang>
This would display:
0 fee fie
1 huff and puff
2 mirror mirror
3 tick tock
choose a number 0..3:
And, if the user responded with 2, would return: <tt>mirror mirror</tt>
--LambertDW 17:59, 8 September 2018 (UTC)
Note: this description of the code is based on an older version (the line below) and is now out of sync with the copy on the main page.
Here are some introductory notes for people not familiar with J, who might care about the J implementation.
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And, as written, it expects the user is displaying the code in a short, wide window (or that they can resize their window that way).
===
The first part of the code to be executed is:
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Here, we have printed each of the composed strings. A subtle distinction here is that they will be displayed before evaluation of the rest of the sentence.
===List indexing===
In all my years, I have never seen:
You have two choices:
0 go
1 don't go
Everybody (except "C" people) are used to choices starting with 1, not zero. Like a book, real people expect
the first page to be 1 (one). Ask anyone for a top ten list, and you won't see 0 --> 9.
[[User:Gerard Schildberger|Gerard Schildberger]] 17:38, 21 January 2011 (UTC)
:But given the topic of this site, it is ''very'' common to have to consider lists with a minimum index of zero as well as one. --[[User:Paddy3118|Paddy3118]] 21:22, 21 January 2011 (UTC)
===prompt user===
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<lang j>
load 'misc'
displayMenu =: i.@# smoutput@,&":&> ' '&,&.>
makeMsg =: 'Choose a number 0..' , ': ',~ ":@<:@#
displayBadNumMsg =: [ smoutput bind 'Please choose a valid number!'
select=: ({::~ _&".@prompt@(makeMsg [ displayMenu)) :: ($:@displayBadNumMsg)
</lang>
:--[[User:Tikkanz|Tikkanz]] 02:46, 15 October 2009 (UTC)
::I have adopted this version, with some minor name changes (and sticking with require instead of load) --[[User:Rdm|Rdm]] 12:43, 26 January 2010 (UTC)
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