It seems not to matter that 1 is in parentheses:
g=:13 :'1 x}y'
1 3 5 g i.10
0 1 2 1 4 1 6 7 8 9
g
4 : '1 x}y'
But hee is a surprise.
Itemize (,:y) shows up.
5!:4 <'g'
┌─ 4
── : ─┴─ ,:'1 x}y'
$'1 x}y'
5
$,:'1 x}y'
1 5
Why is this here?
Linda
-----Original Message-----
From: Programming <[email protected]> On Behalf Of Roger
Hui
Sent: Saturday, July 27, 2019 1:06 AM
To: [email protected]
Subject: Re: [Jprogramming] Learning Tacit Programming
13 : '(1) x}y' or 13 : '1 x}y' can not be made tacit because they use a
function argument (x) as an operand. Similarly 13 : '+/"y x' or 13 : '+/"x y'
can not be made tacit either.
Why not, you might ask? The sequence for an operator is that you _first_
derive a function, and _then_ the function is applied to function arguments x
and/or y . When you say x} or +/"x or +/"y , at that point you don't yet have
the function argument.
On Fri, Jul 26, 2019 at 9:40 PM Devon McCormick <[email protected]> wrote:
> I am intrigued by tacit programming but agree with Henry that you
> should drink the Kool-Aid with slow, measured sips.
>
> I continue to rely heavily on "13 : .." (to the dismay of tacit
> die-hards) but still puzzle over why certain expressions cause it to give up,
> e.g.
>
> 13 : '(1) x}y'
> 4 : '(1) x}y'
>
> Yet this works
> x=. 2 4 6
> y=. i.10
> (1) x}y
> 0 1 1 3 1 5 1 7 8 9
>
> Whereas these do not:
> x ((1) [}]) y
> 0 1 2 3 4 5 6 7 8 9
> x ((1)& [}]) y
> 0 6 2 3 4 5 6 7 8 9
>
>
> On Fri, Jul 26, 2019 at 11:53 PM Henry Rich <[email protected]> wrote:
>
> > Yes, you have to think differently.
> >
> > Please, don't make a fetish of tacit programming. The important
> > thing about becoming a J programmer is training yourself to look at
> > the whole problem rather than working with atoms. That is, getting
> > over the loop mindset.
> >
> > Problem: You have an array a and you want to apply a linear function
> > y=3x+1 to every atom. How do you do it?
> >
> > 0. (3 * a) + 1
> > Bravo! You didn't have to loop. Full marks.
> >
> > 1. 1 + 3 * a
> > Piu bravo! You are thinking right to left.
> >
> > 2. (1 + 3&*) a
> > Bravissimo! You have written a little bit of tacit code. You could
> > also have written (1 + 3 * ]) a
> >
> > 3. 1 3 p. a
> > Congratulations, you have reached master level. Let the interpreter
> > sweat the details.
> >
> >
> > My very first J program was a model of texture processing for a
> > computer-graphics system. I imbibed the tacit liquor too deeply,
> > and wrote the whole thing as a sequence of tacit verbs, 50 of them.
> > It worked. It was absolutely unmaintainable. Don't go there.
> >
> > Use tacit verbs for problems whose spec is mathematically unchangeable.
> > For everything else, use explicit verbs.
> >
> > Henry Rich
> >
> >
> >
> >
> >
> > On 7/26/2019 7:20 PM, The3DSquare Josh Yang wrote:
> > > I was wondering if you guys have any resources for learning tacit
> > > programming in J. I've been struggling with tacit programming,
> > > probably because all the other programming languages are mainly explicit.
> > Something
> > > like "Tacit programming for the explicit programmer" would be
> > > great
> > since I
> > > often fail to derive the tacit equivalent of a series of explicit
> > > eeaxpressions (especially when there are mutable variables).
> > >
> > > I know I need to think differently, but having some guidance would
> > > help greatly.
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> --
>
> Devon McCormick, CFA
>
> Quantitative Consultant
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