When to use broadcasting with . vs map

General Usage
9

If there are multiple arguments, then the behavior of broadcasting and map are quite different:

Broadcasting does… broadcasting, and map does not:

julia> [1] .+ [1, 2, 3]
3-element Array{Int64,1}:
 2
 3
 4

julia> map(+, [1], [1, 2, 3])
1-element Array{Int64,1}:
 2

julia> [1, 1] .+ [1, 2, 3]
ERROR: DimensionMismatch("arrays could not be broadcast to a common size; got a dimension with lengths 2 and 3")

julia> map(+, [1, 1], [1, 2, 3])
2-element Array{Int64,1}:
 2
 3

Also, broadcasting has some “symbolic” definitions for some types:

julia> (1:5) .+ (1:5)
2:2:10

julia> map(+, 1:5, 1:5)
5-element Array{Int64,1}:
  2
  4
  6
  8
 10

Unfortunately I don’t think there is yet a “standard” multi-argument “map” that is requires the arguments to have the same indices. (I asked here.)

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