List ::= < Expr*, >
The use of <, > as both binary operators and list delimiters makes the grammar ambiguous. Section A.4.2 explains how the ambiguity is resolved.
Here, `+' is the concatenation operator on lists.
Eval( <> , C) = emptylist Eval( < Expr > , C) = _list1(Eval( Expr , C))
As defined in Section A.3.4.4, _list1(val) evaluates to a list containing the single value val.