Well.. "such that" sort of implies that u appears on the right and the
value for x on the left. You can do that in J, but you'll need extra
parenthesis, quite often:
such_that=: 2 : '(#~ v) m'
(2+i.20) such_that (1&p:)
2 3 5 7 11 13 17 19
So it seems to me that another name should be used for 1 :'(#~ u) y'
-- perhaps 'selected_from' or something like that?
Still, technically speaking, you are correct, if we ignore the fuzzy
aspects of human language.
Thanks,
--
Raul
On Fri, Dec 26, 2014 at 11:38 AM, Jon Hough <jgho...@outlook.com> wrote:
> #~g seems to work. (Much neater than my code)
> e.g. for my prime set
>
>
>
> g =: 1&p:
>
> (#~g) i. 100
> gives what I want.
>
> So I suppose an adverb of the form #~u for verb u is close to "such that"?
>
>> From: rauldmil...@gmail.com
>> Date: Fri, 26 Dec 2014 11:25:13 -0500
>> To: programm...@jsoftware.com
>> Subject: Re: [Jprogramming] "Such that" syntax in J
>>
>> Now it sounds like you want:
>> (#~ g) x
>>
>> Assuming, of course, that x and g are appropriate.
>>
>> I hope this helps,
>>
>> --
>> Raul
>>
>>
>> On Fri, Dec 26, 2014 at 11:20 AM, Jon Hough <jgho...@outlook.com> wrote:
>> > Thanks for replying.
>> >
>> > I'm confused about two things.
>> >
>> > (1) I'm worried I haven't explained myself well.
>> > I mean I want to find all x given g(x) is true for some function g.
>> >
>> > i.e. the set { x | g(x) is true }
>> > (You may have answered this, I need to read your example more carefully,
>> > but this leads me to problem 2...)
>> >
>> > (2) I don't understand what
>> > ←→
>> > means in terms of J. These are not ASCII characters or J primitives.
>> >
>> > Thanks.
>> >
>> >> Date: Fri, 26 Dec 2014 08:13:40 -0800
>> >> From: rogerhui.can...@gmail.com
>> >> To: programm...@jsoftware.com
>> >> Subject: Re: [Jprogramming] "Such that" syntax in J
>> >>
>> >> f x
>> >>
>> >> where x is an array of all values of interest. For (countably) infinite
>> >> sets you have to express x in terms of i._ . For example, to express the
>> >> Euler product formula for the Riemann zeta function,
>> >>
>> >> +/(1+i._)^-s ←→ */%1-(p:i._)^-s
>> >>
>> >>
>> >>
>> >> On Fri, Dec 26, 2014 at 8:04 AM, Jon Hough <jgho...@outlook.com> wrote:
>> >> >
>> >> > In Haskell (and other languages I'm sure) one can express the idea of
>> >> > "such that" to denote one expression depending on another. In Haskell we
>> >> > can use the syntax:
>> >> >
>> >> > [ f x | x <- xs ]
>> >> >
>> >> > which means
>> >> > "the list of all f x
>> >> > such that x is drawn from xs."
>> >> >
>> >> > So | is syntactically similar to the English "such that". (and very much
>> >> > like | in mathematical sets)
>> >> >
>> >> > I would like to know if J has a construct to express the above Haskell
>> >> > code.
>> >> >
>> >> > Thanks,
>> >> > Jon.
>> >> >
>> >> > ----------------------------------------------------------------------
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>> >> >
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>> >
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>
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