Problem evaluating symbol for macro inside function

General Usage
2

Using eval() inside a macro is almost never necessary, and it’s almost always a signal that something has gone wrong. In this case, there’s no need for eval at all.

Rather than tackling the full version of your code, here’s a simple example of saving a single variable. First, I defined a stub h5write function so I don’t actually have to generate hdf files for testing:

julia> function h5write(filename, data, label)
         println("saving: $data with label $label in file $filename")
       end
h5write (generic function with 1 method)

Then I built a macro to call that function. Note the use of esc(param) to get the un-escaped variable in the expanded code, and the use of QuoteNode to turn a variable into a symbol giving the name of that variable:

julia> macro saving(name, param)
         quote
           h5write(string($name, ".h5"), $(esc(param)), string($(QuoteNode(param))))
         end
       end
@saving (macro with 1 method)

We can verify that this works at local scope:

julia> let 
         local_var = [1, 2, 3]
         @saving "test" local_var
       end
saving: [1, 2, 3] with label local_var in file test.h5

and global scope:

julia> global_var = [1, 2]
2-element Array{Int64,1}:
 1
 2

julia> @saving "test" global_var
saving: [1, 2] with label global_var in file test.h5
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