Import same module as two independent identities

General Usage
,
1

Suppose I have a module

module A

x=1

function set(y)
    global x
    x=y
end

end

Is there a way to import A twice, so that I have two different variables A.x as following

import A as A1
#A1.x=41
A1.set(41)
import A as A2
#A2.x=1024
A2.set(1024)
# A2.x and A1.x are two different variables
2

I don’t believe so, but why do you want this?

I’d recommend using structs:

mutable struct A{T}
    x::T
end
set!(a::A, y) = a.x = y
function Base.getproperty(a::A, s::Symbol)
    s === :set && return Base.Fix1(set!, a)
    getfield(a, s)
end

yielding

julia> a1 = A(4)
A{Int64}(4)

julia> a1.set(6)
6

julia> a1
A{Int64}(6)

I’d also recommend not doing the set thing with getproperty and just calling set! directly.

1 Like
3

I am using the TaylorSeries package for Taylor polynomial expansions.

There is a type TaylorN in this package, which describes a polynomial with N variable. The number of variables and orders can be set via

using TaylorSeries
x, y = set_variables("x y", order=2);

However, I would like to obtain a composite type, like TaylorN{TaylorN{Float64}}. The outer TaylorN has different orders and number of variables with inner TaylorN.

Let me give you an example
f(x,y)=a_{00}+a_{10}x+a_{01}y+a_{20}x^2+a_{11}xy+a_{02}y^2
The coefficients are controlled by 3 knobs,
a_{ij}(k_1,k_2,k_3)=c_{000}+c_{100}k_1+c_{010}k_2+c_{001}k_3

The following code doesn’t work,

using TaylorSeries
x1,x2=set_variables("x1 x2",numvars=2,order=5)
y1,y2,y3=set_variables("y1 y2 y3",numvars=3,order=4) 
# x1 and x2 become invalid, because the above command 
#      changes the maximum order and number of variables

Therefore, I wonder if there is a way so that

import TaylorSeries as TS1
import TaylorSeries as TS2
x1,x2=TS1.set_variables("x1 x2",numvars=2,order=5)
y1,y2,y3=TS2.set_variables("y1 y2 y3",numvars=3,order=4)
# typeof(x1)=TS1.TaylorN{Float64}
# typeof(y1)=TS2.TaylorN{Float64}
# both x1 and y1 are valid, and their types--- TS1.TalorN and TS2.TaylorN---are different

I have a stupid method to solve this. But it seems weird.

module TS1
      include("path to TaylorSeries.jl")
end

module TS2
      include("path to TaylorSeries.jl")
end

# Now TaylorN in TS1 and TaylorN in TS2 are two different structs
#      and they have their own method of set_variables
4

Hi!

The way TaylorSeries works internally for the multivariable case, is by defining some internal tables which depend on the maximum degree of your polynomials and on the number of variables; those tables are some constant (but mutable) internal globals. That’s the reason that, if you run twice set_variables you overwrite the previous meaning of the maximum order and number of variables.

A possibility to achieve what you are after (including the variable order) is to use nested Taylor1 variables. So a polynomial of order two is a polynomial in one variable whose coefficients are polynomials in one variable, a similarly to more variables, as you describe above. While the possibility exists, we haven’t had the time to polish it and make it nicer for the user; see WIP: Nested Taylors by blas-ko · Pull Request #126 · JuliaDiff/TaylorSeries.jl · GitHub. Moreover, we have doubts that this is as performant as the TaylorN approach. In any case, I am interested in your solution!

2 Likes
5

Thanks for your information.