[Oberon] Linked list of binary trees plus what ?

[Chris Glur]

The EditKeys utility which effectively allows defining 'hot-keys' [macro 
definitions of user chosen strings are activated by the <insert> key]
seems worth investigating.

 In order to understand certain parts of the manual/Tool  Eg.:
  "Text stretches are pushed on a parameter stack when processed.
	Built-in functions may pop parameter(s) from that stack.

	^0	pops a parameter and causes textual insertion.
	^1	pops a parameter and inserts the corresponding ascii character.
..etc.",   I looked at the source code.

But the data-structures confuse me.     Here are some:--

		SequenceDesc = RECORD
			next: Sequence;   <-- linked list
			sym: INTEGER;
			cmd: CHAR;
			def: Definition;
			stretch: Texts.Buffer
		END;
		
		DefinitionDesc = RECORD
			left, right: Definition;  <-- binary tree
			in: BOOLEAN;
			trig: Ident;  <-- ARRAY IdentLen OF CHAR
			seq: Sequence
		END;

It seems to me that 'Sequence' is a linked list of Definitions
with nodes: sym, cmd, stretch.
And that Definition is a binary tree.
But the confusing/un-natural thing is that Definition's nodes
have also further Sequence-linkedLists !

Q - is this correct ?

I'm guessing that the data structures employed are those 
which naturally occur for macro/compilers/?? 

Can anybody give me a clue of how to better understand 
this application ?  It originates from 1992 and the full use of
it's features may be very usefull.

== Chris Glur.