Julia: how do I convert a symbolic expression to a function?

Question

I have created a symbolic expression using the SymPy package (https://github.com/jverzani/SymPy.jl). I want to now find the roots of that expression using the Roots package

Answer 1

With Julia 0.6 this works straight out of box:

julia> using SymPy, Roots

julia> x = Sym("x")
x

julia> expr = sin(x)
sin(x)

julia> fzeros(expr, -10, 10)
7-element Array{Float64,1}:
 -9.42478
 -6.28319
 -3.14159
  0.0
  3.14159
  6.28319
  9.42478

But it's a lot slower than pure Julia solution. Here are some benchmarks I ran with BenchmarkTools:

Naive Solution (6.8s):

fzeros(expr, -10, 10)

Pure Julia (1.5ms):

fzeros(x-> sin(x), -10, 10)

Semi-Naive (7.6ms):

fzeros(Function(expr), -10, 10)

Explicit Conversion (3.8ms):

expr2 = Function(expr)
fzeros(expr2, -10, 10)