Mutation

[Andrew Justin Blumberg]

> 
> > Regarding the use of mutation, isn't it pretty common once you start
> > using arrays?  When doing large data analyses in Lisp, I've had to
> > replace lists of numbers with typed arrays, and changed computations
> > to all work in place so as to reduce garbage creation.  This is to
> > increase efficiency, and often helps alot (can give a factor of 2 or 3
> > speedup, or even make an intractible problem tractible).  What sort of
> > effects are the anti-mutation proposals going to have on this?
> > 
> > -- 
> > Harvey J. Stein
> 
> The problem with functional objects is indeed functional arrays.  You
> have to have some way to initialize them.  One way to do this is to
> have them start life as mutable arrays, and then at some point you
> 'freeze' them into immutable arrays.  The problem with this approach
> is that it 'surprises' the person still holding onto a pointer to the
> old 'mutable' array.  These semantics are very unpleasant because they
> violate the constancy of type.

consider the following situation :

i'm reading text into a buffer.  i'm going to want to compute based on the
text, but i don't want to keep it.  thus, when processing a lot of files i 
use a single buffer and write over it repeatedly to cut down on gratuitous
consing.  

how would this be resolved in a functional object framework?

								- andrew