Element-wise addition operator

[Zizheng Tai]

Hi everyone,

I'm trying out Breeze and notice that both + and :+ can be used for element-wise addition of vectors. The :+ operator seems more consistent with other element-wise operators (:*, :/, etc.) though. Also, / and :/ seem to have the same effect, too. Is there any difference between them? Which one should I prefer?

Thanks,

Zizheng

[David Hall]

Hi Zizheng,

The operators without ":" are "shaped", while the ones with ":" are elementwise. It happens that addition of vectors corresponds to elementwise addition, which is why they're the same. (This is usually true, of course...) 

If I knew what I knew now, I would probably not allow / to mean elementwise division (except by scalar). I may still do that after a suitable deprecation cycle. 

I personally usually use + over :+, and similarly with other operators when they have the same meaning. The main reason for this is operator precedence. All operators starting with : (and not ending in =) have the same precedence in scala, which is highly inconvenient in this case, though I can't fault them for choosing a relatively simple rule.

Note that in master and snapshots, the :+ style operators are deprecated because of the confusing precedence. We're switching to +:+, etc, which are a bit more verbose, but don't have precedence problems.

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