New issue 874: YTArray multiplication is not associative with respect to code units https://bitbucket.org/yt_analysis/yt/issue/874/ytarray-multiplication-is-not...

John ZuHone:

Test case, on a FLASH dataset:

``` #!python

...

...

a = yt.YTArray([1,2,3], "cm") b = ds.arr([1,2,3], "code_length")

...

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a*b

YTArray([ 1., 4., 9.]) cm*code_length

...

...

b*a

YTArray([ 1., 4., 9.]) cm*code_length

...

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(b*a).in_units("code_length**2")

YTArray([ 1., 4., 9.]) code_length**2

...

...

(a*b).in_units("code_length**2")

UnitParseError: Could not find unit symbol 'code_length' in the provided symbols. ```

Presumably this is because the final ``YTArray`` takes the unit registry from the first of the two in the binary operation. This is a simple and irrelevant example, but it illustrates the problem. Not sure how important this is.

Responsible: ngoldbaum