Re: [boost] [Graph] suggestion: rename distance_zero() to distance_identity()

From: Andrew Sutton (asutton_at_[hidden])
Date: 2007-09-18 21:40:58

> As part of the revision of the graph library, I suggest that this
> named parameter be relabeled to distance_identity().  That would
> capture its general meaning, regardless of the nature of the combine
> method.

Brook,

I mostly agree, but I think we can do better too. One of the reasons  
that it probably took the name distance_zero() is that there haven't  
been many motivating examples of non-additive combinations of  
distance (and hence identities).

I'm wondering if it might not be worthwhile to build simple  
structures that provide the function types and constants for these  
algorithms rather than specifying them as distinct parameters. For  
the common case, these would simply default to the basic additive  
operations and identities but could be easily overridden.

I'm sure there are some nice mathematical terms and properties that  
could describe these (monoids, semigroups, group, etc.). I'm not a  
mathematician, so I don't know for sure.

Andrew Sutton
asutton_at_[hidden]