Thanks, now I understand what to do. However, I don't understand your
comment about "...the SAGE coercion model". What is an example of
that - the sage integers?
-M. Hampton
On Sep 25, 12:10 pm, "Mike Hansen" <[EMAIL PROTECTED]> wrote:
> Since I don't think that graphs and polytopes fall under the SAGE
> coercion model, overloading operators is pretty straightforward. You
> just need to define the __add__ method in your class. x + y will call
> x.__add__(y).
>
> sage: class Foo:
> ....: def __add__(self, y):
> ....: return 42
> ....:
> sage: a = Foo()
> sage: b = Foo()
> sage: a + b
> 42
> sage: b + a
> 42
>
> Note that you'll want to do some type-checking so that y is what you
> actually think it should be.
>
> --Mike
>
> On 9/25/07, Hamptonio <[EMAIL PROTECTED]> wrote:
>
>
>
> > I would appreciate any tips on how to extend the + operator in this
> > way, since I would like to implement Minkowski sums of polytopes and
> > this is natural notation for that.
> > Marshall
>
> > On Sep 25, 10:37 am, "Mike Hansen" <[EMAIL PROTECTED]> wrote:
> > > In SAGE, '+' is used for union of sets. For example,
>
> > > sage: a = Set([1,2])
> > > sage: b = Set([2,3])
> > > sage: a+b
> > > {1, 2, 3}
>
> > > Since currently, + is not defined for graphs, it'd be a natural choice.
>
> > > --Mike
>
> > > On 9/25/07, Jason Grout <[EMAIL PROTECTED]> wrote:
>
> > > > I'm thinking more about how to make the Graph class easy to use. One
> > > > thing that crops up is that the operations that combine graphs only
> > > > combine two graphs at a time (e.g., g.union(h), where g and h are
> > > > graphs).
>
> > > > Is there a way to define an infix operator that would allow one to say:
>
> > > > g union h union i union j union k?
>
> > > > I could do it with something like:
>
> > > > reduce(lambda x,y: x.union(y), [g,h,i,j,k])
>
> > > > But that doesn't seem as clear as the infix things above.
>
> > > > For reference, Mathematica allows an operator in backticks to be applied
> > > > to its surrounding arguments, so the equivalent operation above would
> > > > be:
>
> > > > g `union` h `union` i `union` j `union` k
>
> > > > And of course, you can set whether the operator is left-associative or
> > > > right-associative.
>
> > > > Of course, one solution is to use a for loop:
>
> > > > newgraph=Graph()
> > > > for graph in [g,h,i,j,k]:
> > > > newgraph.union(graph)
>
> > > > But that seems a lot clunkier than the infix expression above.
>
> > > > I guess another solution is to return the new graph from the union, so
> > > > that you could do:
>
> > > > g.union(h).union(i).union(j)
>
> > > > Thoughts?
>
> > > > -Jason
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