Re: [pygame] vector type: mutable or immutable

[Stuart Axon <stu.axon+pygame@xxxxxxxxx>]

I guess mutable is more consistent with the rest of the api (things
like rect IIRC)

2009/5/1 Lorenz Quack <don@xxxxxxxxxxxxxxxxx>:
> Hi
>
> as a follow up to the "API draft for vector type" I would like to discuss
> the merits of having a mutable or immutable vector type.
>
>
> Arguments for an immutable vector type:
>
> Brian Fisher pointed out two advantages of immutable vector types:
> 1) they prevent bugs in programs like the following (adopted from Brian):
>> class Angel(object)
>>     def __init__(self, offset):
>>         self.offset = offset
>>
>> t = Angel()
>> halo_pos = t.offset
>> halo_pos.y -= 5  # BUG: this changes the offset in t
>
> 2) if vectors are immutable you can use them as keys in dicts
>
>
>
> Arguments for a mutable vector type:
>
> 1) operations such as rotate() and scale_to_length() are more elegant when
> operation in-place. for immutable types you would have to do "v =
> v.rotate()" or use a module level rotate function "v =
> pygame.math.rotate_vector(v)" or something similar.
>
> 2) a priori I would expect mutable vectors to perform better than immutable
> ones because you don't have to create new objects for every operation.
>
>
>
> So are there anymore arguments?
> And where do people stand on this issue?
>
>
> yours
>
> //Lorenz
>