Compound variable highlighting

Compound variables are special, in the sense that they have two simultaneous aspects: they are, at the same time, variables, and indexed stem references. The Rexx Highlighter honors this duality by returning compound variables as single elements that include a number of sub-parts; you can decide which of the two aspects of a compound variable will determine the highlighting mode.

  -- As an indexed reference
  Say Matrix.1.2A.j..

  -- As a whole
  Say Matrix.1.2A.j..

You can select the compound variable highlighting mode using the compound=true|false attribute on the rexx fenced code block marker. The default is to highlight all the components individually.

```rexx {compound=true}
(rexx code goes here)
```

```rexx {compound=false}
(rexx code goes here)
```

When highlighted as a single element, a compound variable will have a class of .EL.COMPOUND_VARIABLE or, if the variable is exposed (i.e., it is an instance variable), of .EL.EXPOSED_COMPOUND_VARIABLE.

::Method myMethod
  Expose var stem.
  local = var + 1
  Say stem.12..2E.var.local

When taking sub-parts into account (which is the default), different highlighting attributes will be used for the stem name (a .EL.STEM_VARIABLE or a .EL.EXPOSED_STEM_VARIABLE) and for all the components of its tail. The first dot in a compound variable is part of the stem name. The rest of the symbol, the tail, is an arbitrary sequence of: variables (either local, .EL.SIMPLE_VARIABLE, or exposed, .EL.EXPOSED_SIMPLE_VARIABLE); signless integers (.EL.INTEGER_NUMBER); pure dotless constant symbols (.EL.SYMBOL_LITERAL), and tail separators dots (.EL.TAIL_SEPARATOR).