Evaluation in calling scope?

General Usage
13

it’s because const is missing, see here

so, here’s the solution for calling scope evaluation, despite the fact that only relatively simple expression could be handled:

function expr2fun(ex)
    vars = getvars(ex)
    return eval(:($Expr(:meta, :inline); $vars -> $ex) )   # is it the correct way to inline???
end

getvars(ex) = Expr(:tuple, _getvars(ex)...)
_getvars(ex::Symbol) = [ex]
function _getvars(ex::Expr)
    vars = Symbol[]
    if ex.head == :call
        for arg in ex.args[2:end]
            append!(vars, _getvars(arg) )
        end
    end
    return unique(vars)
end
_getvars(ex) = Symbol[]  # fallback

ex = :(x * (y - x) - (x * y - 2) )
const fun = expr2fun(ex)        # const is needed to avoid warntype !

@inline f1(x, y) = x * (y - x) - (x * y - 2)
@inline f2(x ,y) = fun(x, y)    # calling slope evaluation

julia> f1(1, 2) == f2(1, 2)
true
julia> @btime f1(1, 2);
  0.022 ns (0 allocations: 0 bytes)
julia> @btime f2(1, 2);
  0.022 ns (0 allocations: 0 bytes)
julia> @btime fun(1, 2);
  0.022 ns (0 allocations: 0 bytes)

hope it helps.

1 Like