Implementation of linear algebra for ArrayPartition

[vnvasquez]

The following MWE pertains to the implementation of vec: basically, if the elements inside the ArrayPartition are vectors, all works as it should. However, if the ArrayPartition contents are matrices then the size of the return from vec is incorrect.

using NLsolve
using RecursiveArrayTools

function mymodel(F, vars)
    for i in 1:2
        x = vars.x[i]    
        F.x[i][1,1] = (x[1,1]+3)*(x[1,2]^3-7)+18.0
        F.x[i][1,2] = sin(x[1,2]*exp(x[1,1])-1)
        F.x[i][2,1] = (x[2,1]+3)*(x[2,2]^3-7)+19.0
        F.x[i][2,2] = sin(x[2,2]*exp(x[2,1])-3)
    end
end

# To show that the function works
F = ArrayPartition([0.0 0.0; 0.0 0.0],[0.0 0.0; 0.0 0.0])
u0= ArrayPartition([0.1 1.2; 0.1 1.2], [0.1 1.2; 0.1 1.2])
result = mymodel(F, u0) 
vec(u0)

# To show the NLsolve error that results with ArrayPartition: 
nlsolve(mymodel, u0)

This may be related to the way that linear algebra was implemented for the fix to this issue: #44 (comment)

[ChrisRackauckas]

Fixed by #106 . I'll get that merged and tagged once tests pass.