map(Function, AbstractArray) and siblings use type of first output to determine type of all output

[WestleyArgentum]

It seems that some effort was put into implementing map this way, so I figured I should post before putting time towards a pull request.

I'm assuming the reason for this is speed. I'd be interested to know, has anyone has profiled it done this way vs producing Any arrays?

I think it seems unlikely at first that the function you pass into map will return values of different types... but this has come up a couple times with strings for me. If the first string I output is plain ascii and then the second is utf8, I'm hosed.

ex:

julia> d = { "a" => "ascii", "u" => "u†f∞" }
{"u"=>"u†f∞","a"=>"ascii"}

julia> map((a)->d[a], ["a", "u"])
ERROR: invalid ASCII sequence

Maybe the case for strings can be special cased, or maybe map should just produce Any arrays.

[mlubin]

dup of #210 (old issue)

[WestleyArgentum]

Ah, you're right, and I think Stephan's comment in #670 really sums it up.