On 29 May 2016 at 02:04, marcel.taeumel <Marcel.Taeumel at hpi.de> wrote:

> Kjell Godo wrote
> > Object>>recurse: aZeroInputValuable"ThatReturnsATwoInputValuable"
> >
> > ^( aZeroInputValuable value
> >  ) value:( self )value:[ :anObject | anObject recurse: aZeroInputValuable
> > ]
> >
> > "Object>>recurse:
> >
> > does for recursion what >>do: does for iteration
> >
> > it enables any Object O to do recursion
> > Without writing a new recursive method in the Class of O
> >
> > It does this even if the
> > BlockClosures in this version of Smalltalk being used
> > Can only do tail recursion accurately
> > Like in Dolphin Smalltalk 6
> >
> > You call it like
> >
> > ( anObject recurse:[[ :anobject :recurse |
> >        ( anobject someChildren collect:[ :child |
> >               ( something something ).
> >               ( ( recurse value:( child something ) ) something )
> >               ]
> >        ) asSomeObjectSomething
> > ]] )
> >
> > ok
> > So i haven't actually tried it yet
> > so i do not actually know if it actually works
> > so it's too hot off the presses for that
> > because I'm more into a math major than physics
> > i guess i always like math way better
> > and so i have a tendency to say      that has already been shown
> > but i can't see how it can fail
> > So i am putting it out there right now without testing it first
> > each recursion creates a new twoInputValuable
> > and the >>recurse: method keeps getting called
> > from inside of itself
> >
> > so i think it works
> >
> > but i guess you have to try it to find out
> >
> > if you can figure an easier way
> > or why it can't work
> > then please show it
> >
> > i have been trying to do this for a long time
> > and it shocks me that it's so small     must be something wrong in there
> > so if you easily find a better way
> > or that it's no way at all
> > then i missed it and I'm too early
> > and I'm semi mal informed
> > ie stupeid
> > and I'm a baaad scientrist       cepting I'm not one
> > et all
> > not quite easily done
> >
> > Kjell E Godo"
>
> Hi Kjell,
>
> I suppose that this code is a suggestion for Trunk? If you did not try it
> out, where does it come from? Dolphin Smalltalk 6?
>
> It does look like a valuable addition to me. Although, I read it like
> re-curse and thought of Monkey Island and LeChuck. :-D Are there other
> words
> for this?
>
> #combine:
> #doRecursive:
>
> Anyway, it seems to work for Fibonacci:
>
> 6 recurse: [[:number :step |
>    number caseOf: {
>       [0] -> [1].
>       [1] -> [1].
>    } otherwise: [
>       (step value: number - 2)
>          + (step value: number - 1)]]].
>

I bet you'd like it a whole lot less if someone used it and you had to
debug it. I've done things that were at most half as tricky as this [1],
and it was NOT fun to debug. In fact, trying to do so breaks the debugger
if you do the obvious thing and try debug-edit-and-resume, and I still owe
a fix for that...

frank

[1]
https://github.com/frankshearar/Parsing-Derivatives/blob/master/Derivatives/DerivingParser.st#L199..L226


> Best,
> Marcel
>
>
>
> --
> View this message in context:
> http://forum.world.st/The-Object-recurse-Method-tp4897901p4897988.html
> Sent from the Squeak - Dev mailing list archive at Nabble.com.
>
>
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