[NTG-context] How to check if a register item appears in a specific chapter, or not?

5 Apr 2025

      \setevalue{standard1}{Students will learn how to navigate the library catalog efficiently.}
\setevalue{standard2}{Students will learn how to use a library card to access various services.}
\setevalue{standard3}{Students will learn to locate and select appropriate resources across different media.}
\setevalue{standard4}{Students will learn to utilize digital databases for academic research.}
\setevalue{standard5}{Students will learn to operate self-checkout stations for streamlined borrowing.}
\setevalue{standard6}{Students will learn to manage due dates and renew borrowed materials responsibly.}
\setevalue{standard7}{Students will learn the fundamentals of the library classification system.}
\setevalue{standard8}{Students will learn to evaluate information sources for credibility and relevance.}
\setevalue{standard9}{Students will learn to use reference materials to support academic inquiries.}
\setevalue{standard10}{Students will learn to adhere to library policies and ethical usage guidelines.}
\setevalue{standard11}{Students will learn to reserve study areas and meeting spaces effectively.}
\setevalue{standard12}{Students will learn to access and navigate digital library resources.}
\setevalue{standard13}{Students will learn to engage with library programs and community events.}
\setevalue{standard14}{Students will learn to utilize interlibrary loan services for extended research.}
\setevalue{standard15}{Students will learn to apply proper citation methods for materials sourced from the library.}

\defineregister[learnedshort][compress=yes]
\setupregister[learnedshort][style=sansbold, textstyle=slanted, n=1, pagenumber=yes, indicator=no]
%
\defineregister[learnedlong][compress=yes]
\setupregister[learnedlong][style=sansbold, textstyle=slanted, n=1, pagenumber=yes, indicator=no]
%
\define[1]\learned{%
    \learnedshort{#1}%
    \learnedlong{\getvalue{#1}}%
}
%

\starttext

    \startchapter[title={Trees}]
        \placeregister[learnedlong][way=bychapter, criterium=chapter]

        \section{Content}    
        \learned{standard1}
        \input knuth
    \stopchapter

    \startchapter[title={Birds}]
        \placeregister[learnedlong][way=bychapter, criterium=chapter]

        \section{Content}
        \learned{standard8}
        \learned{standard16}
        \learned{standard6}
        \input knuth
    \stopchapter

    \startchapter[title={Squirrels}]
        \placeregister[learnedlong][way=bychapter, criterium=chapter]

        \section{Content}
        \learned{standard2}
        \learned{standard15}
        \learned{standard13}
        \learned{standard9}
        \input knuth
    \stopchapter

\stoptext

I have some code like the above, used in a textbook. This is as best as I could simplify it.

First, there are values that define a series of state standards. These list what students need to know according to state law.

Next, theres two registers that keeps track of every time the standard is taught in the text. For instance, in the third chapter, "standard2" is covered.

It then has a list at the start of evey chapter listing the standards that appeared; and I could similarly add an index at the end listing page numbers.

My problem is, I need to make a better visual for readers for seeing where the standards appear. Here's a table:

\setupcolors[state=start]
\setupTABLE[frame=on, align=middle, option=stretch]

\bTABLE[split=yes]
  % Header row: empty first cell then Chapters 1–15
  \bTR
    \bTD[align=middle] {} \eTD
    \bTD[align=middle] Chapters 1 \eTD
    \bTD[align=middle] Chapters 2 \eTD
    \bTD[align=middle] Chapters 3 \eTD
    \bTD[align=middle] Chapters 4 \eTD
    \bTD[align=middle] Chapters 5 \eTD
    \bTD[align=middle] Chapters 6 \eTD
    \bTD[align=middle] Chapters 7 \eTD
    \bTD[align=middle] Chapters 8 \eTD
    \bTD[align=middle] Chapters 9 \eTD
    \bTD[align=middle] Chapters 10 \eTD
    \bTD[align=middle] Chapters 11 \eTD
    \bTD[align=middle] Chapters 12 \eTD
    \bTD[align=middle] Chapters 13 \eTD
    \bTD[align=middle] Chapters 14 \eTD
    \bTD[align=middle] Chapters 15 \eTD
  \eTR
  % Data rows: one row per standard (standard1 to standard15)
  \bTR
    \bTD[align=middle] standard1 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard2 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard3 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard4 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard5 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard6 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard7 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard8 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard9 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard10 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard11 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard12 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard13 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard14 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
  \bTR
    \bTD[align=middle] standard15 \eTD
    \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD \bTD \eTD
  \eTR
\eTABLE

Basically, I need a way for the code to check, "Does standard1 appear in chapter 1?" If yes, put a checkmark. If not, leave blank.

if standard1 is in chapter1then    print "✓"else    print ""
How can I setup such a check?

--Joel