using a name macro for variables from a functions inputs

Question

If I have 2 variables, a=[.3, .2, .4]; b=[.1, .2, .3]; I can create a string with the name of the variable using a macro:

macro varname(arg)
    string(arg)
end

@varname(a)

now say I have a function and I want to pass it an arbitrary number of arguments and use the actual variable names that are being given to function to create dictionary keys:

function test(arguments...)
    Dict(Symbol(@varname(i)) => i for i in arguments)
end

this won't work because @varname will take i and create "i", so for example:

out=test(a,b)

the output I would like is:

Dict("a" => [.3, .2, .4], "b" => [.1, .2, .3])

Is there a way to achieve this behavior?

If arguments is a variable length tuple of positional parameters then they don't have names. If on the other hand, the definition is function test(;arguments...) which makes arguments named parameters, then Dict(a[1]=>a[2] for a in arguments) should usually work (except for edge cases with argument names repeating etc). — Dan Getz
– Dan Getz, Commented Sep 13, 2017 at 22:52

Chris Rackauckas · Accepted Answer · 2017-09-13 16:30:13Z

2

Parameters.jl has such a macro. It works like this:

using Parameters
d = Dict{Symbol,Any}(:a=>5.0,:b=>2,:c=>"Hi!")
@unpack a, c = d
a == 5.0 #true
c == "Hi!" #true

d = Dict{Symbol,Any}()
@pack d = a, c
d # Dict{Symbol,Any}(:a=>5.0,:c=>"Hi!")

If you want to know how it's done, just check its source:

https://github.com/mauro3/Parameters.jl/blob/v0.7.3/src/Parameters.jl#L594

answered Sep 13, 2017 at 16:30

Chris Rackauckas

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