[e-lang] Syntax: Trailing commas in lists, and line breaks in list-patterns

[Kevin Reid]

I would like E to allow trailing commas in comma-separated lists, so I 
can write code like

   [
     one,
     two,
     three,
   ]

without needing to remember to add a comma to the formerly-last item 
when I add another item.

A related issue: The list- (and map-) pattern, unlike the 
list-expression, does not permit a line break after the leading [, 
requiring me to write:

   def [ \
     one,
     two,
     three
   ] := ...

-- 
Kevin Reid