Function handle

[blegat]

Is it possible to create a function handle ? I tried the following but it doesn't seem to work

julia> a = MATLAB.mat"@(t, y) 2*t"
inary
Error using save
Unable to save variable 'ans' of class 'function_handle' to STDIO.
 
ERROR: MATLAB.MEngineError("failed to get variable ans from MATLAB session")
Stacktrace:
 [1] get_mvariable(session::MSession, name::Symbol)
   @ MATLAB ~/.julia/dev/MATLAB/src/engine.jl:164
 [2] get_mvariable
   @ MATLAB ~/.julia/dev/MATLAB/src/engine.jl:168 [inlined]
 [3] get_variable(name::Symbol)
   @ MATLAB ~/.julia/dev/MATLAB/src/engine.jl:170
 [4] top-level scope
   @ ~/.julia/dev/MATLAB/src/matstr.jl:169

However, the following works

julia> eval_string(MSession(), "ode45(@(t,y) 2*t, [0,5], 0)");

Ideally would need to create a function handle that is accessing a large Julia matrix. So while this seems to do the trick, I'm worried that it's just copying the content of the matrix in the string so that won't be so good with a large matrix

julia> x = [1, 2]
2-element Vector{Int64}:
 1
 2

julia> eval_string(MSession(), "ode45(@(t,y) sum($x)*t, [0,5], 0)");

This also does not work as it seems to not be able to represent the function handle in Julia

julia> MATLAB.mxcall(:ode45, MATLAB.mat"@(t, y) 2*t", [0, 5], 0)
Fontconfig warning: "/usr/share/fontconfig/conf.avail/05-reset-dirs-sample.conf", line 6: unknown element "reset-dirs"
Fontconfig warning: "/usr/share/fontconfig/conf.avail/05-reset-dirs-sample.conf", line 6: unknown element "reset-dirs"
Error using save
Unable to save variable 'ans' of class 'function_handle' to STDIO.
 
ERROR: MATLAB.MEngineError("failed to get variable ans from MATLAB session")
Stacktrace:
 [1] get_mvariable(session::MSession, name::Symbol)
   @ MATLAB ~/.julia/dev/MATLAB/src/engine.jl:164
 [2] get_mvariable
   @ MATLAB ~/.julia/dev/MATLAB/src/engine.jl:168 [inlined]
 [3] get_variable(name::Symbol)
   @ MATLAB ~/.julia/dev/MATLAB/src/engine.jl:170
 [4] top-level scope
   @ ~/.julia/dev/MATLAB/src/matstr.jl:169

Is there any way to call a MATLAB function that requires function handles and that would scale for large matrix.
For the context, this is the function I'd like to call https://github.com/alpyurtsever/SketchyCGAL/blob/master/solver/CGAL.m and Primitive1, Primitive2 and Primitive3 are the function handles

[tqml]

Hey @blegat !
At the moment, MATLAB.jl uses the C-API from matlab engine, which as it seems, does not to support copying complex types (Classes, Function Handles) from MATLAB.

Ideally would need to create a function handle that is accessing a large Julia matrix. So while this seems to do the trick, I'm worried that it's just copying the content of the matrix in the string so that won't be so good with a large matrix

In your example this is correct, so you shouldn't do it that way. Instead the correct way to do this is to copy your Julia array to MATLAB using @mput or put_variable, executing the matlab code using eval_string and then get the result using mget.
This process is automated when using a mat"" string.

So ideally do something like:

mat"""
result = ode45(@(t,y) sum($x)*t, [0,5], 0)
$result_x = result.x
$result_y = result.y
"""

this will expand to the following julia code:

put_variable(<random_name>, x)
eval_string("result = ode45(@(t,y) sum(<random_name>)*t, [0,5], 0)")
eval_string("<random_name2> = result.x")
eval_string("<random_name3> = result.y")
result_x = get_variable("<random_name2>")
result_y = get_variable("<random_name3>")
eval_string("clear <random_name> <random_name2> <random_name3>")

Also note that there is a size limit of 2GB that can be transferred via the MATLAB engine API.
So if your matrices exceed that limit, you might need to break them into pieces, transfer individually and then concat them in MATLAB again (or write them to mat file, and read the file from MATLAB)

Hope this helps :)

[blegat]

Thanks a lot!