Clarification: How filter operator, :filter, and :map run prefixes work?

[Mohammad]

Example demo

To show the application of this discussion, see the Simple Pagination Two example below.
It accept a filter (with any complexity) and produces a list with a header contains alphabetical index buttons! On click the output will be limited to titles prefixed with that letter.

Code

\define simple-pagination-two(scope:"[all[tiddlers]!is[system]]")
<$let
    letters      = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    cond         = "[all[tiddlers]] +$scope$ +[uppercase[]prefix<currentTiddler>]"
    tempTid      = "$:/temp/pagination"
    titlePrefix  = {{{ [<tempTid>get[text]] }}}
    listfilter   = "[uppercase[]prefix<titlePrefix>]"
    selStyle     = "[<currentTiddler>match<titlePrefix>then[font-weight:bold;color:red;]]"
>

<!-- create header -->
<$list filter="[<letters>split[]filter<cond>]">
<$button style="color:navy;margin:1px;width:2em;height:1.8em;cursor:pointer;">
<span style={{{[subfilter<selStyle>]}}} ><$text text=<<currentTiddler>> /></span>
<$action-setfield $tiddler=<<tempTid>> text=<<currentTiddler>> />
</$button>
</$list>

<!-- generate output -->
<$list 
  filter="[subfilter<__scope__>filter<listfilter>sort[title]]"
  template="$:/core/ui/ListItemTemplate" 
/>
</$let>
\end

To give a try

• download Simple Pagination Two.json (1.2 KB)
• drag and drop into https://tiddlywiki.com
• open Simple Pagination Two

Remarks

• Two filter operator is used, cond and listfilter
• Note to the usecases in
  • filter="[<letters>split[]filter<cond>]"> and
  • filter="[subfilter<__scope__>filter<listfilter>sort[title]]"
• Some css styles have been used as cosmetic!

Screencast

In the below an example the macro is called with

<<simple-pagination-two "[tag[Filter Operators]] [tag[Filter Run Prefix]]">>

which produces