How do I create a function from an expression

General Usage
21

Actually, I have just figured out to do this macro without Base.invokelatest and updated SyntaxTree :

julia> using SyntaxTree, BenchmarkTools

julia> g = genfun(:(-(cos(x))),[:x])
(::#3) (generic function with 1 method)

julia> @btime $g(1.0)
  40.790 ns (0 allocations: 0 bytes)
-0.5403023058681398

julia> f = @genfun -cos(x) [x]
(::#3) (generic function with 1 method)

julia> @btime $f(1.0)
  40.801 ns (0 allocations: 0 bytes)
-0.5403023058681398

Now the evaluation is much faster because it is not using Base.invokelatest anymore. The implementation

macro genfun(expr,args)
    :($(Expr(:tuple,args.args...))->$expr)
end

genfun(expr,args) = :(@genfun $expr [$(args...)]) |> eval

is very simple to write in Julia in the end, it is now part of the SyntaxTree package.

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