Creating Custom Syntax Highlighting in Quarto

When I tried to write a summary in quarto of the theoratical programming lecture, I wanted to include syntaxt highligthing for so called ram programs:

<!-- ````ram{code-line-numbers=false}
# f(x, y, z) = z + x ⋅ y
0   R3 ← 1
# Begin der Schleife
1   IF R1 = 0 GOTO 3
2   R2 ← R2 + R0
3   R1 ← R1 - R3
4   GOTO 1
# Ende der Schleife
5   R0 ← R2
6   STOP 
```-->

to create costom syntax highlighing on has to define it inside an xml file.

here are some other examples of establish laguages: https://github.com/KDE/syntax-highlighting/tree/master/data/syntax

I made a very simple and easy to change file

ram.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE language>

<language name="RAM" version="1" kateversion="5.62" section="RAM" extensions="*.ram;*.ram" mimetype="text/ram;" author="Daniel Schwarzenbach" license="MIT">
  <highlighting>

    <list name="Operators">
      <item>←</item>
      <item>=</item>
      <item>&lt;</item>
      <item>&gt;</item>
      <item>≥</item>
      <item>≤</item>
    </list>

    <list name="Keywords">
      <item>IF</item>
      <item>GOTO</item>
      <item>STOP</item>
    </list>
    
    <contexts>
      <context attribute="Normal Text" lineEndContext="#stay" name="Normal">
        <DetectSpaces attribute="Normal Text" />
        
        <keyword attribute="Keyword" context="#stay" String="Keywords" />
        
        <RegExpr attribute="Register" context="#stay" String="R+[0-9]+" />
        <RegExpr attribute="LineNumber" context="#stay" String="[0-9]{1,3}   " />
        <RegExpr attribute="Number" context="#stay" String="[0-9]+" />
        <RegExpr attribute="Comment" String="#.*$"/>
        <RegExpr attribute="Operator" String="\+|-|="/>
        <keyword attribute="Operator" context="#stay" String="Operators" />
      </context>
    </contexts>

    <itemDatas>
      <itemData name="Normal Text"            defStyleNum="dsNormal" />
      <itemData name="Keyword"                defStyleNum="dsKeyword" />
      <itemData name="Operator"               defStyleNum="dsFunction" />
      <itemData name="Register"               defStyleNum="dsDataType" />
      <itemData name="LineNumber"             defStyleNum="dsNormal" />
      <itemData name="Number"                 defStyleNum="dsBaseN" />
      <itemData name="Comment"                defStyleNum="dsComment" />
    </itemDatas>
  </highlighting>
</language>

finaly one has to include this file inside the quarto settings:

syntax-definitions: 
      - ram.xml

now your custom syntax highlighting should be working

# f(x, y, z) = z + x ⋅ y
0   R3 ← 1
# Begin der Schleife
1   IF R1 = 0 GOTO 3
2   R2 ← R2 + R0
3   R1 ← R1 - R3
4   GOTO 1
# Ende der Schleife
5   R0 ← R2
6   STOP