Hi, I would do something like this:
f=: +:
cond=: 100<{:
repuntil =: 2 : '((<:@{. , u@}.)`] @. v )^:(0<{.)^:_'
f repuntil cond 20 1
0 32
f repuntil cond 20 1
13 128
the first item tells you whether:
- if 0: iterations ended due to hitting the limit (first item of argument);
or
- if > 0, the condition became true.
The agenda (@.) construct is just a way of making the left verb argument to
the left-most ^: return the same twice, which triggers the end of the
iteration by ^: _ .
Good luck exploring J, it'll keep being interesting for long ;).
Best regards,
Jan-Pieter
On Tue, May 26, 2020, 12:04 'Rob Hodgkinson' via Programming <
[email protected]> wrote:
> I don’t agree, it does not proceed further.
>
> ([x] u^:v^:_ y) will actually stop when v returns 0 (does not skip or
> continue executing)
>
> Here is a simple way to confirm this using a function f to do 2&* but
> which also uses ’smoutput’ to output to the session log (print intermediate
> results).
>
> f=: verb define
> smoutput r=:2*y
> r
> )
>
> f 5
> 10 NB. Intermediate print using smoutput
> 10. NB. Result of f
>
> Test it…
> a=:f 5
> 5. NB. It still prints within f via smoutput
>
> So now …
> f^:(10>])^:3 ] 1
> 2 }
> 4 } Intermediates from smoutpout (f called 3 times)
> 8 }
> 8 NB. Result returned (ran to completion)
> f^:(10>])^:4 ] 1
> 2 }
> 4 } Intermediates from smoutpoutn (f called 4 times)
> 8 }
> 16 }
> 16 NB. Result returned (ran to completion)
> f^:(10>])^:8 ] 1
> 2 }
> 4 } Intermediates from smoutput (f called 4 times)
> 8 }
> 16 }
> 16 NB. Result returned (aborted, so it stopped short
> and did not proceed further)
>
> HTH, Rob
>
>
> > On 26 May 2020, at 6:40 pm, Anton Wallgren <[email protected]> wrote:
> >
> > On closer inspection, f^:v^:n doesn’t seem to work (as I want it to).
> What it does is to skip evaluation each time v y returns 0. While this
> would work in my situation, as the stopping condition would remain true, it
> would of course be unnecessary (and inefficient) to keep checking this for
> the remainder of the iterations.
> >
> > Thanks, Anton Wallgren
>
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