[m-dev.] Re: For review: changes to graph.m

[Andrew Bromage]

G'day.

I wrote:

> > Ignoring the possibility of changing between representations depending
> > on the amount of data stored (eg represent sets by lists for "small"  
> > data sets and trees for "big" sets), this is a perfect application of
> > existential types, which are on the "to do" list.

Peter Schachte replied:

> How do existential types help with this?

Having a type class `set(T)' helps in that you have one interface
which can be implemented in many ways.  However you need existential
types if, for example, you wanted to create a list of sets.

Cheers,
Andrew Bromage