[Bf-python] mathutil PyNumberMethods behaving badly

[Campbell Barton]

Agree

foo = 1
bar =  -foo
bar==1

Vectors should act the same

Id opt for not depricating -vec , but as you say making -vec the same as 
vec.negated()
 
Ill have a shot at this, is there any problem with commiting after 2.42 
freeze (a few days) - or do you want to review a patch.?
- Cam


Gilbert, Joseph T. wrote:
> We don't need -vec no. It is a shorthand operator. However, I thought it
> would be nicer for the end-user.
>
> However, now that we have 2 versions of negate(), it's debatable if we
> want to deprecate -vec because it may lead to confusion as to what it's
> doing.
> If we don't want to deprecate it, my suggestion is to give it the
> behavior of vector.negated() - i.e. return a modified copy.
>
> As for the confusing part:
> Right now you can get the proposed behavior of vector.negated() by
> doing:
>
> Vector(vec).negate()
>
> however, most people will do something like this:
>
> Vector(vec.negate())
>
> which will modify the original vector as well.
>
> There needs to be a way to get python-safe copies of wrapped data.
>
> Another option might be to add a method to make the object a safe copy
> if it is not already. Like Local() or Safe_Copy() or something....
>
>
> -----Original Message-----
> From: bf-python-bounces at projects.blender.org
> [mailto:bf-python-bounces at projects.blender.org] On Behalf Of Ken Hughes
> Sent: Friday, July 21, 2006 3:17 AM
> To: Blender Foundation Python list
> Subject: Re: [Bf-python] mathutil PyNumberMethods behaving badly
>
> Personally I think having -vec, vec.negate() and veg.negated() is a bit 
> like flammable, inflammable and non-flammable.  A little confusing and 
> somewhat redundant.  I like the math operations, but don't think we need
>
> a duplicate method for them (if I understand Joseph's suggestion).
>
> Also, I was just pointing out a bug.  It needs to be fixed prior to 
> 2.43, but that's a long way off.  If any of the API rewrite is going to 
> be done prior to 2.43, I'd like to see the discussion first before the 
> implementation.
>
> $0.02 -- Ken
>
> Campbell Barton wrote:
>   
>> Hi Joseph, read through this and It sounds like what we want
>>
>> Think I suggested that in the first place but we can take it further.
>> invert() inverted() - inverted would be realy usefull because at the 
>> moment You have to copy a matrix and then invert it wich can be a bit
>>     
> wordy
>   
>> omat_i=Blender.Mathutils.Matrix( ob.matrixLocal )  # (wrapped)
>> omat_i.invert()
>>
>> - could be replaced with
>>
>> omat_i= ob.matrixLocal.inverted()
>>
>> Do you want help with this or would you rather do yourself?
>> Id like to have this for 2.43
>>
>> - Cam
>>
>>
>> Gilbert, Joseph T. wrote:
>>     
>>> This was something we discussed a few months ago.
>>> The proposal was to have a 2 methods. One which returns a
>>>       
> self-modified
>   
>>> reference and another that returns a modified-copy.
>>>
>>> Example:
>>> ref_to_orig_vector = vector.negate()
>>> new_mod_vector = vector.negated()
>>>
>>> The -vec are shortcuts in pymath. They should be bound to either of
>>>       
> the
>   
>>> 2 above methods. It would make sense to have them be bound to the
>>> version that returns a new_modified_vector for safety.
>>>
>>> To keep the current API "negate" would continue to do what it does
>>>       
> now.
>   
>>> We would need to add "negated", etc. for all the self-modifying
>>>       
> methods
>   
>>> of all the py math objects that require them.
>>>
>>> -----Original Message-----
>>> From: bf-python-bounces at projects.blender.org
>>> [mailto:bf-python-bounces at projects.blender.org] On Behalf Of Ken
>>>       
> Hughes
>   
>>> Sent: Thursday, July 20, 2006 2:29 PM
>>> To: Blender Foundation Python list
>>> Subject: [Bf-python] mathutil PyNumberMethods behaving badly
>>>
>>> Cam discovered a problem in the mathutils with expressions like this:
>>>
>>> me = Mesh.Get('Cube')
>>> x = -me.verts[0].co
>>> print x
>>> print me.verts[0].co
>>>
>>> You get this:
>>>
>>> [-0.565980, -1.386673, 0.000000](vector)
>>> [-0.565980, -1.386673, 0.000000](vector)
>>>
>>> Joseph put in code which modifies the original object, since script 
>>> users wanted to concatenate operations, but I don't think we really
>>>       
> want
>   
>>> to this with math operations (i.e., PyNumberMethods).
>>>
>>> Seems to me we need two type of operations in mathutils: one modify 
>>> the original data and return it and ones that don't (now on three: 1,
>>>       
>
>   
>>> 2, 3, "Duh").  Obviously the math operations shouldn't do this, but 
>>> looks like
>>>
>>> we need to "un-deprecate" some of the original methods like
>>> vector.negate()
>>>
>>> Ken
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>>>   
>>>       
>>     
>
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>   


-- 
Campbell J Barton

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