[Compiler-sig] changes to ast

[Mark Hammond]

> These changes made the code faster

How much faster?  Significantly?  The speed of this is still my biggest
issue, and may get around to looking at the C implemented compiler tools
announced here (by the Wing people?) not too long ago...


> but I wonder how many people depended on the old
> sequence-style access protocol.

.NET does, but I am happy to move to this new scheme - the code is
definitely clearer without using node indexing...

Mark.