Explanation of attrs item in rules

[moritz-gross]

@daisy/mathcat-translators

Some rules use an item called attrs, usually nested within intent.

here is a full example

-
  name: geometry-ray
  tag: mover
  match:
    - "*[2][self::m:mo][.='→'] and"  # u2192
    - "*[1][self::m:mrow][count(*)=3 and "
    - "     *[1][self::m:mi and translate(., 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', '') = ''] and"
    - "     *[2][self::m:mo and (.='\u2062' or .='\u2063')] and"
    - "     *[3][self::m:mi and translate(., 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', '') = '']"
    - "                  ]"
  replace:
  - intent:
      name: "ray"
      attrs: "data-intent-property='concat(data-intent-property, \":prefix:\")'"
      children:
      - x: "*[1]/*[1]"
      - x: "*[1]/*[3]"

I could not find any documentation on this. I assume it stands for "attributes"?
My questions include:

• what kinds of attributes can be set here?
• can it only be used within intent ?
• the main use is data-intent-property I guess?
• ...

[kudala-bharani]

Yes, attrs means attributes to set on the element produced by intent. I checked the current implementation in Intent::build and Intent::replace.

• It is currently a field inside intent, not a standalone command under replace.

• Its value is a string of assignments like name='XPath expression', with spaces between multiple assignments. Each expression is evaluated against the generated intent element, converted to a string, and assigned to that attribute.

• It isn't restricted to data-intent-property. For example, the standalone Laplacian rule uses:

  attrs: "id='@id'"

data-intent-property is a common use, and it gets extra handling to normalize fixity properties such as :prefix:. Other attributes go through the ordinary assignment path; setting them doesn't necessarily give them any special meaning to MathCAT.

One small XPath detail in your example: data-intent-property without @ selects a child element, not an attribute. If the intention is to append to the existing attribute, that expression would be concat(@data-intent-property, ":prefix:").