It's less about the array ordering and more about the fact that mathematically
the row index comes before the column index and doing it the other way would be
very confusing. It's a shame these don't match, but there's not much to do
about it.
> On May 16, 2014, at 4:57 PM, francois.fay...@gmail.com wrote:
>
> I am very new to Julia, but here is my guess :
> - for i = , j =
> should be the same as
> for i =
> for j =
> It would be awkward to have something else.
> - For comprehensions, the order is the other way around because matrices are
> stored in Julia in column order as in Fortran (and maybe Matlab) as opposed
> to C. Therefore, ordering the comprehension that way make the filling of the
> array cache-friendly.
>
> François
>
>> On Friday, May 16, 2014 10:52:22 PM UTC+2, Peter Simon wrote:
>> Comprehensions and for loops do not perform nested looping in the same order:
>>
>> julia> [begin println((i,j)); (i,j) end for i = 1:3, j = 1:4]
>> (1,1)
>> (2,1)
>> (3,1)
>> (1,2)
>> (2,2)
>> (3,2)
>> (1,3)
>> (2,3)
>> (3,3)
>> (1,4)
>> (2,4)
>> (3,4)
>> 3x4 Array{(Int64,Int64),2}:
>> (1,1) (1,2) (1,3) (1,4)
>> (2,1) (2,2) (2,3) (2,4)
>> (3,1) (3,2) (3,3) (3,4)
>>
>>
>> julia> for i = 1:3, j=1:4
>> println((i,j))
>> end
>> (1,1)
>> (1,2)
>> (1,3)
>> (1,4)
>> (2,1)
>> (2,2)
>> (2,3)
>> (2,4)
>> (3,1)
>> (3,2)
>> (3,3)
>> (3,4)
>>
>>
>>
>> Just wondering what the rationale is for this difference.
>>
>> --Peter
