Evaluate flag

[proy87]

It would be good if evaluate was stored as class attribute, so I could check whether I have unevaluated expression.

[proy87]

Also, Add(0,1,2,3,evaluate=False).args gives 1,2,3, because args = [a for a in args if a is not cls.identity] removes it.

[oscarbenjamin]

Really I'd like to get rid of evaluate=False. I think that not evaluating should be the default.

The other issue is fixed in master from #19450:

In [79]: Add(0,1,2,3,evaluate=False).args                                                                                                      
Out[79]: (0, 1, 2, 3)

[proy87]

@oscarbenjamin , but we need to track whether expression is evaluated. For example, I want to keep order of args unchanged when printing, if an expression is unevaluated.

[oscarbenjamin]

I don't see why we don't just print the args in order all the time

[proy87]

Because for me it is more natural n-1 then -1+n

[oscarbenjamin]

That particular example is better but there are others e.g.:

In [40]: -y + z                                                                                                                                
Out[40]: -y + z

In [41]: _.args                                                                                                                                
Out[41]: (z, -y)

[proy87]

Possibly, the sorting of args should be improved.