How to feval?

[J Luis]

Hi,

I need to convert this piece of Matlab code

          [ps, orig_path] = feval(str2func(test), out_path);

where 'test' is the name of a function and 'out_path' it unique input argument. I have read and re-read the eval function and for once it's clear for me how it works (sorry, I find this sentence highly cryptic "Evaluate an expression in the given module and return the result" ) but worst, I don't see anywhere how it could call a function with input arguments.

How can I achieve the same result in Julia?
 
Thanks.

[Kristoffer Carlsson]

Maybe

julia> eval(Symbol("sin"))(5.0)
-0.9589242746631385

Not sure if this is the best solution.

[J Luis]

Thanks, at least it's a place to start.

[Alex Ames]

You could define your own feval:

feval(fn_str, args...) = eval(parse(fn_str))(args...)

This has the advantage of accepting anonymous functions and multiple arguments if necessary:

julia> feval("sin",5.0)

-0.9589242746631385

julia> fn_str = "a_plus_b(a,b) = a + b"

"a_plus_b(a,b) = a + b"

julia> feval(fn_str,2,3)

5

[Stefan Karpinski]

This will not be fast. It's also wildly insecure if the string come from an external source. I'd strongly recommend figuring out a different approach to what you're doing, but it's hard to provide guidance without more context.

[J Luis]

Speed is not critical here. I am porting this script

   http://gmt.soest.hawaii.edu/projects/gmt-matlab-octave-api/repository/changes/trunk/src/gmtest.m

that will call the test scripts that live, as for example, here

    http://gmt.soest.hawaii.edu/projects/gmt/repository/show/branches/5.2.0/doc/scripts/ml

and compare the produced output with the reference PS file that is also in the testing dirs.

If it works, as I hope and will test later. It's good enough for me but off course faster alternatives are always wellcome.

Thanks

[J Luis]

Anyway, unfortunately none of the above solutions work for files. If the file is called "GMT_insert.jl", and is in the path, I get variations around (+ file extension - file extension) of

ERROR: UndefVarError: GMT_insert not defined

[Stefan Karpinski]

Julia doesn't identify functions and files the way Matlab does. You can just load the file by name.