On Monday, January 26, 2015 at 12:02:10 PM UTC-5, Wai Yip Tung wrote:
>
> I'm trying to construct a list of list and do some operation on it. In
> Python I would do
>
> In [7]: ll = [[1,2],[1,2,3],[7]]
>
> Say I want to sort them by the length of the list, many function accepts a
> `key` parameter. In this case I want the `key` to be `len`.
>
> In [8]: max(ll, key=len)
> Out[8]: [1, 2, 3]
>
> In [9]: sorted(ll, key=len)
> Out[9]: [[7], [1, 2], [1, 2, 3]]
>
> In Julia, if I enter the literal [[1,2],[1,2,3],[7]], then are join to
> together into a long list. Through many trial and error I found a way by
>
> ll = (Array)[[1,2],[1,2,3],[7]]
>
> What is the proper way to construct a list of list?
>
> Secondly, Julia's sort support a `by` parameter that does what `key` do in
> Python. But there is no equivalent in `maximum`. What is the recommended
> way to find the longest list in the data structure?
>
> Wai Yip
>
I think it may be more idiomatic to initialize the array as:
ll = Array{Int,1}[[1,2],[1,2,3],[7]]
if all elements will be 1d arrays of type Int. You could also use:
ll = Vector{Int}[[1,2],[1,2,3],[7]]
as a short hand. If the arrays are going to be of arbitrary type:
ll = Any[[1,2],[1,2,3],[7]]
Josh
