position in a list

[Mohammad]

I have a list of tiddlers, I iterate over the list and I want to know if an item is before or after the selected item!

How to do this?

--Mohammad

[Mohammad]

A partial solution

<$set name=selected value=7>

<$list filter="[range[1,10]]"  variable="item" >

<$list filter="[range[1,10]allbefore<selected>] +[prefix<item>]">

<<currentTiddler>>  is before selected item: <<selected>><br>

</$list>

</$list>

</$set>

This works, any better idea? Any TW intrinsic solution?

--Mohammad

[Mat]

Maybe you can treat the list like a string and cut the list at the selected item (listbefore[]) and then see if the item is in the remaining list - if it is not, then it was before otherwise it was after.

<:-)

[TonyM]

Mohammad

This is not the full answer but counting the items in a list can give you helpful information. The set widgets select parameter and the rest operator amongst others all provide the components to do this and do it well.

Perhaps store the number of items from count then use the select parameter to iterate each item. The position in the list will then be a number and last time I looked 4 was after 3, and 3 before 4 so the relation ship is obviouse

Tony

[Mark S.]

<$set name=selected value=7>
<$list filter="[range[1,10]]"  variable="item" >

<$list filter="[range[1,10]allbefore<selected>] -[range[1,10]allbefore<item>] -[range[1,10]allafter<item>]">
<<item>>  is before selected item: <<selected>><br>
</$list>
</$list>
</$set>

[Mark S.]

I think this answers your question as described in your text -- note that it specifies both numbers to compare. It uses pre20

<$vars selected=7 whereami=8>
<$list filter="[range[1,10]allbefore<selected>match<whereami>]">
<<whereami>>  is before selected item <<selected>><br>
</$list>
<$list filter="[range[1,10]allafter<selected>match<whereami>]">
<<whereami>>  is after selected item <<selected>><br>
</$list>
</$vars>

On Friday, August 2, 2019 at 5:41:33 AM UTC-7, Mohammad wrote:

[TonyM]

Mohammad,

I would have thought all you need is in the order operators especially

after	find which input title follows a specified one
before	find which input title precedes a specified one

https://tiddlywiki.com/?home#Filter%20Operators

I have not used these extensively yet but I believe they hold the key to problems like your own, keep in mind you can use these to establish one set, and subtract that from another set. These should provide all the elements for lists, queues head and tail operations and alot more.

For example

using first then storing rest, then using first on the rest allows you to step through every member and allows you to see what is coming. You could count how many items remain in rest for a progress indicator and more....

Also

The range operator documentation should also be extended to show how to provide values to the <begin>,<end>,<step> parameters from fields and variables.

<$set name=number-or-members value={{{ [filter] +count[]] }}}>

the range[1,number-or-members]

Second section in table is Order Operators, note that N is a number you can provide.

after	find which input title follows a specified one
before	find which input title precedes a specified one
bf	same as rest
butfirst	same as rest
butlast	discard the last N input titles
first	select the first N input titles
last	select the last N input titles
limit	select the first or last N input titles	✓	!
next	find which titles in a list field follow the input ones
nsort	sort the input by number field		!
nsortcs	sort the input titles by number field, treating upper and lower case as different		!
nth	select the Nth input title
order	selectively reverse the input list	✓
previous	find which titles in a list field precede the input ones
rest	discard the first N input titles
reverse	reverse the order of the input titles
sort	sort the input by text field	✓	!
sortan	sort the input by text field considering them as alphanumerics	✓	!
sortcs	sort the input by text field, treating upper and lower case as different

Regards

Tony

[Mohammad]

Smart solution Mark!

Added to TW-Scripts.