Convert array to tuple

[John Lynch]

I'm working on a ref card for people who know Python moving to Julila

I can convert a tuple xx to an array with  aa = [xx...]


but how to do I convert a 1d array like [1:5] to a tuple?
and/or how do I flatten an array down to a collection of elements


Thanks

[John Lynch]

Sorry.  Thought I was posting in users.

[Stefan Karpinski]

julia> tuple([1:5]...)

(1,2,3,4,5)

[John Lynch]

Thanks.  Thats probably the only combo I didn't try.

What is the term for / meaning of ... please?

[John Lynch]

Also, the other two things I've been having trouble mapping are these slices.

Do we have an equivalent (from Python)?

s[i:j:k] slice with stride k

s[::2]; s[::-1] every 2nd Element / reverse s

[Stefan Karpinski]

The middle of a range is the stride, which can be negative:

julia> [1:1:5]

5-element Array{Int64,1}:

 1

 2

 3

 4

 5

julia> [1:2:5]

3-element Array{Int64,1}:

 1

 3

 5

julia> [0:2:5]

3-element Array{Int64,1}:

 0

 2

 4

julia> [5:-1:1]

5-element Array{Int64,1}:

 5

 4

 3

 2

 1

julia> [5:-1:0]

6-element Array{Int64,1}:

 5

 4

 3

 2

 1

 0

julia> [5:-2:0]

3-element Array{Int64,1}:

 5

 3

 1

julia> [5:-3:0]

2-element Array{Int64,1}:

 5

 2

[Avik Sengupta]

On Friday, 18 October 2013 07:26:32 UTC+1, John Lynch wrote: 

 

What is the term for / meaning of ... please?

The ... in a function call  flattens iterables into its  elements, to be merged with other arguments in a function call into a single tuple. It only works in a function call syntax (and not as an expression), hence in the example above Stefan takes the result via a the tuple() constructor. A  ... in a function defintion denotes a varargs.

More details here: http://docs.julialang.org/en/latest/manual/functions/#varargs-functions

This kind of a thing is typicalyl called a splat or a destructing operator, I think. 

[John Lynch]

Thanks Avik, Stefan,

Splat I like.

[Stefan Karpinski]

Yes, I generally pronounce it as "dots" or "splat", although "splat" is written other ways in other languages, .e.g prefix "*" in python.