You can box y, repeat it with dyadic #, and then raze the boxes:
3 ([: ; [#<@]) 'hi'
hihihi
3 ([: ; [#<@]) 1 2 3
1 2 3 1 2 3 1 2 3
3 {{ ; x # <y }} 1 2 3
1 2 3 1 2 3 1 2 3
The 'J By Point and Click' lab introduces a graphical debugger that you could
use in place of manually added debugging output.
I don't really follow your (d;d) question but you could define either verb in
terms of the other:
repeat =: [: ; [#<@]
2 repeat 'x'
xx
repeat2 =: 0&{:: repeat 1&{::
repeat2 2;'x'
xx
repeat3 =: repeat2@;
2 repeat3 'x'
xx
In general I'd not worry too much about which is right, and instead be quick to
notice when a choice leads to more trouble when used.
------- Original Message -------
On Thursday, January 27th, 2022 at 7:23 AM, Pawel Jakubas
<[email protected]> wrote:
> Dear J enthusiasts,
>
> I am defining `x repeat y` function, that is appending y to itself x times.
>
> And defined something like below (on intention like that to ask a couple of
>
> questions).
>
> f=: 4 : 0
>
> assert (x < 10)
>
> segment=.>0{y
>
> if. (x = 1) do. (>1{y) else. (x-1) f (segment;( (>1{y),segment) ) end.
>
> )
>
> d
>
> 1 2 3
>
> 1 f (d;d)
>
> 1 2 3
>
> 2 f (d;d)
>
> 1 2 3 1 2 3
>
> 3 f (d;d)
>
> 1 2 3 1 2 3 1 2 3
>
> 1. Is there a way to customize assert message. So instead of
>
> 11 f (d;d)
>
> |assertion failure: assert
>
> | assert(x<10)
>
> have for example message "only x less than 10 is accepted"
> 2. How to introduce debugs? For example I would like to print x as f
>
> executes
> 3. Do we have by the way `repeat` in J as I try to define?
> 4. I intentionally defined f like above as it needs (d;d) as y. Let's
>
> assume I want higher level `repeat` dyad that is
>
> x repeat d
>
> and
>
> defines inside `f` dyad as above and calls it
>
> x f (d;d)
>
> What are good practices to to separate x,y from repeat and not to mix them
>
> in the defined function f (ie. have them decoupled).
>
> Thanks in advance and cheers,
>
> Pawel
>
> For information about J forums see http://www.jsoftware.com/forums.htm
----------------------------------------------------------------------
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