CODEWITHSUNDEEP
julia
AVA
AVA

Reputation: 2568

How to run constructed commands in julia?

I am having package names in an array, trying to execute "using <PACKAGE_NAME>" with the following code in deps.jl:

#! /opt/julia/julia-1.1.0/bin/Julia
packages =["MbedTLS","HTTP"]
for package in packages
try
("using "package) 
cath err
println("$err")
end
end

executing, $/home/julia/deps.jl, throws error "cannot juxtapose string literal". Please help me!

Upvotes: 0

Views: 124

Answers (1)

hckr
hckr

Reputation: 5583

You can use symbols and @eval macro to do this. @eval macro runs the given expression at the top level.

packages = [:MbedTLS, :HTTP] # use symbols instead of strings
for package in packages
    try
        @eval(using $package) 
    catch err
        println("$err")
    end
end

If you need to use strings for some reason, you can first convert it to a Symbol and use @eval with the results.

packages = ["MbedTLS", "HTTP"]
for package in packages
    try
        @eval(using $(Symbol(package))) 
    catch err
        println("$err")
    end
end

"using "package tries to create the string literal "using" to juxtapose it to variable package (i.e. like 5 in x=3; b = 5x). String literal juxtaposition is a syntax error in Julia 1.0. Even if it wasn't a syntax error, I do not recall that it would be used for running expressions.

Please see Metaprogramming section in Julia documentation for more about creating and manipulating code from within Julia.

Upvotes: 3

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