[julia-users] Linear algebra question (shift rows to the right)

[Alex M]

Sorry if it's out of topic of the group.

What is the name of the operation which makes transformation :

[a b c; d e f; g h t] -> [a b c; 0 d e; 0 0 g]

It shifts rows to the right and fills left trailing values by zeros.

Re: [julia-users] What is the difference between { } and [ ]? What is {}?

[Alex M]

Thanks!

Does it mean that now curly braces { } are not used anymore in the version 
0.4?


On Friday, September 11, 2015 at 5:53:19 PM UTC+2, Yichao Yu wrote:
>
> On Fri, Sep 11, 2015 at 11:39 AM, Alex M <updat...@gmail.com > 
> wrote: 
> > Hello, 
> > I am learning Julia. 
> > 
> > Both are arrays but of different types: 
> > 
> > julia> {} 
> > 0-element Array{Any,1} 
> > 
> > julia> [] 
> > 0-element Array{None,1} 
> > 
> > 
> > julia> [] == {} 
> > true 
> > 
> > Now I am trying to push new data : 
> > 
> > 
> > julia> a = [] 
> > julia> b = {} 
> > 
> > 
> > julia> push!(a,"y") 
> > ERROR: [] cannot grow. Instead, initialize the array with "T[]", where T 
> is 
> > the desired element type. 
> >  in push! at array.jl:457 (repeats 2 times) 
> > 
> > 
> > But for [] it works: 
> > 
> > julia> push!(b,"y") 
> > 1-element Array{Any,1}: 
> >  "y" 
> > 
> > 
> > Also using {} I can create Dictionary: 
> > 
> > julia> {"a" => 3} 
> > Dict{Any,Any} with 1 entry: 
> >   "a" => 3 
> > 
> > 
> > Now I am very confused. 
> > 
> > 1) What is the meaning of { } ? is it a dictionary constructor or an 
> array 
> > constructor of type Any ? 
>
> It was `Any[]` for 0.3. Deprecated for 0.4 
>
> > 2) Why can't I push into [ ] ? 
>
> Because the type is None. `[]` on 0.4 returns `Array{Any,1}` and that 
> isn't a problem anymore. 
>
> > 
> > Thank you in advance! 
>

[julia-users] What is the difference between { } and [ ]? What is {}?

[Alex M]

Hello,
I am learning Julia.

Both are arrays but of different types:

julia> {}
0-element *Array{Any,1}*

julia> []
0-element *Array{None,1}*


julia> [] == {}
*true *

Now I am trying to push new data :
 

julia> a = []
julia> b = {}


julia> *push!(a,"y")*
*ERROR: *[] cannot grow. Instead, initialize the array with "T[]", where T 
is the desired element type.
 in push! at array.jl:457 (repeats 2 times)


But for [] it works:

julia> *push!(b,"y")*
1-element Array{Any,1}:
 "y"


Also using {} I can create Dictionary:

julia> *{"a" => 3}*
*Dict{Any,Any} with 1 entry:*
  "a" => 3


Now I am very confused.

1) What is the meaning of { } ? is it a dictionary constructor or an array 
constructor of type Any ?
2) Why can't I push into [ ] ?

Thank you in advance! 

[julia-users] Error in the Dict type declaration

[Alex M]

Hello,

I am trying to attach the type for a variable like that:

julia> a::Dict{String, Array{Float64}} = { "y" => Float64[1.0, 2.0]}
ERROR: type: typeassert: expected Dict{String,Array{Float64,N}}, got 
Array{Float64,1}

julia> a::Dict{String, Array{Float64}} = { "y" => [1.0, 2.0]}
ERROR: type: typeassert: expected Dict{String,Array{Float64,N}}, got 
Array{Float64,1}

Why is it an error?

Best regards,
Alex