particles attributes now return reference instead of copy

[ipelupessy]

ce7207c5da1b25103eecda7104628b65646f8270 has changed p.x from returning a copy to returning a reference to data. This introduces different behaviour for in-memory sets and in-code sets, difference between grids and Particles, and issues with subsets:

p=Particles(5)

p.x=range(5) 
tmp=p.x
print tmp is p.x

#behaviour of index expressions
tmp=p[::2].x

p.x=p.x+1

print tmp == p[::2].x

tmp=p.x[::2]
p.x=p.x+1

print tmp == p[::2].x


# behaviour of grids
p=Grid(5)
p.x=range(5) | units.m
tmp=p.x
print tmp is p.x

gives on 4168ed99b8ccc163a5f9311722c6f28b7c1aeee4:

False
[False False False]
[False False False]
False

while on ce7207c5da1b25103eecda7104628b65646f8270:

True
[False False False]
[ True  True  True]
False

[rieder]

Which of the two is the desired behaviour?

[ipelupessy]

for me consistency between in-memory and code sets is most important..

[ipelupessy]

still relevant

[stale[bot]]

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