How can I limit the number of recrusions in a macro using recursions.

[Jan]

Hello,
want to show the title of a chain of tiddlers which mention the next on in a field called thread.
This works fine like this

\define plotchain()
<$set name="chain" value="JJ/Das merkwürdige Tier">
$(chain)$
<<reku>>
</$set>
\end
\define chainer() [[$(chain)$]]
\define reku()
<$list filter="[list[$(chain)$!!thread]] [list[$(chain)$!!storylink]]" variable="chain">
<<chainer>>
<<reku>>
</$list>
\end

<$vars chain="JJ/Das merkwürdige Tier">
<<chainer>>
<<reku>>
</$vars>

But if someone builds a cirle this crashes the wiki.
Is there a way of limiting recursions e.g. by using a filter with math-operators?

Thanks!
Jan

[TonyM]

Jan

Here is a quick high level answer, let me know if you want more details.

There are existing examples out there that avoid this like the standard TOC however one method that comes to mind is as you iterate each title add it to a variable "all members" (even a data tiddler) and before doing so check it is not already named in that variable. You can just change the action for it to do nothing, the recursion will then move on with the next in line.

I have an algorithm (in a button) where I actually place  the "all members" variable into each tiddler as a field called branch-branchname in your case this would be 

thread-threadname thus each tiddler knows all its predecessors. The thread name can be based on the first tiddler. This would allow multiple threads to cross the same tiddlers without interfering with the other thread. Since you know all the members of the thread you could store the full thread in any tiddler.

Just some ideas

Tony

[Jan]

Hi Tony,
yes I need the details, I already thought of the toc-macro...but I could not figure out how limiting recursions is done there.
I think this is the more promising approach.

Thanks! Jan

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[TonyM]

Jan,

Is this a flat list of tiddlers? Perhaps recursion is not needed.

If you had a seperate tiddler, lets call it path, and all tiddlers involved would be tagged with path then <<tag path>> will allow you to view and reorder the list. Your next and previous buttons could iterate this list of path tagged tiddlers, identifying what next and previous is and providing a button to move in either direction. The value is you cannot add the same tiddler twice to this list of tagged tiddlers thus you will never encounter a circle. 

Tony

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[Jan]

Hi Tony,
I need to generate a (flat) list by using a recursive macro.
I found a somewhat bizarre solution:
------------

\define plotchain()
<$set name="chain" value="JJ/Das merkwürdige Tier">
$(chain)$
<<reku>>
</$set>
\end
\define chainer() [[$(chain)$]]
\define reku()
<$list filter="[list[$(chain)$!!thread]] [list[$(chain)$!!storylink]]" variable="chain">

<$list filter="[<limiter>addprefix[x]!prefix[xxxxxxxxxxxx]]" variable="limiter">
<<limiter>> <!--This is not necessary but shows that it works....-->
<<chain>>
<<reku>>
</$list>
</$list>
\end

<$vars chain="JJ/Das merkwürdige Tier" marker="y">
<<chainer>>
<<reku>>
</$vars>
--------------------------

I could not figure out another way to do so.
Strange but Yeahhh!

Jan

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[TonyM]

Jan

Bimlases kin operator can generate flat lists from a hierarchy all by itself in a single filter.

Have a look at it.

Tony

[Mark S.]

This does literally what you asked for, though I'm not sure that's what you meant:

\define recurseme(yourvar,count)
<$list filter="[<__count__>!regexp[^0$]]" emptyMessage="TOO MANY RECURSIONS!" >
I'm doing important things here! <br/>
<$set name="count" filter="[<__count__>subtract[1]]" select=0>
<$macrocall $name=recurseme yourvar="Stuff" count=<<count>>/>
</$set>
</$list>
\end

<<recurseme "more" "5">>

Put your own code where it says "I'm doing important stuff here." (Be sure to back up first).

Good luck!

[Mohammad]

Sounds great Mark!

I think it is not far from writing Fibonacci sequence in Tiddlywiki :-)

--Mohammad

[Mark S.]

\define fibber(last,next,count)
<$list filter="[<__count__>!regexp[^0$]]" emptyMessage="<<last>> <<next>>" >

<$set name="count" filter="[<__count__>subtract[1]]" select=0>

<$set name="next" filter="[<__last__>add<__next__>]" select=0>
<<__last__>> <$macrocall $name=fibber last=<<__next__>> next=<<next>> count=<<count>>/>
</$set></$set>
</$list>
\end

<<fibber "0" "1" "6">>

[Mark S.]

Oops. Here's a fix for fibonacci

\define fibber(last,next,count)<$list filter="[<__count__>!regexp[^0$]]" emptyMessage="<<__last__>> <<__next__>>" >

<$set name="count" filter="[<__count__>subtract[1]]" select=0>
<$set name="next" filter="[<__last__>add<__next__>]" select=0>
<<__last__>> <$macrocall $name=fibber last=<<__next__>> next=<<next>> count=<<count>>/>
</$set></$set>
</$list>
\end


<<fibber "0" "1" "6">>

[Mohammad]

Hi Mark!

 This is amazing! Fibonacci sequence code is among the benchmark code to show how efficient a language support the recursive operation.

 This code shows Tiddlywiki scripting language is powerful and of course shows your talent :-)

--Mohammad

[Mohammad]

Added to TW-Scripts.

https://kookma.github.io/TW-Scripts/#Fibonacci%20Sequence

--Mohammad

[Jan]

Hi Mark!
Thanks, that is much more elegant than my "prefix"-workarround which I posted!

Jan


Am 18.10.2019 um 06:17 schrieb Mohammad:

Added to TW-Scripts.

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[Mohammad]

Resend for email users!

The entry in TW-Scripts

https://kookma.github.io/TW-Scripts/#Fibonacci%20Sequence

--Mohammad

[@TiddlyTweeter]

Mark S.' Fibonacci sequence macro is really interesting & clever.

I'm getting interested in the idea of using macros similar to that to select Tiddlers to create "sample sub-series".

An example would be for a screenplay you want to analyse. Its well known that most mainstream movies have a "three-act" structure and sub-structures/patterns within them. 

It might be interesting to sample a screenplay that is in, say, 1,000 tiddlers, using mathematical patterns to better understand its screenplay structure.

That sampling would not be from a Fibonacci sequence, but seeing it, I realised we can now do "sample patterns" macros quite elegantly. So far I been using random sampling. This opens a better way.

Early thoughts. I'll formulate a better question about this at some point.

Best wishes

Josiah