CODEWITHSUNDEEP
juliasympy
Felix
Felix

Reputation: 83

LoadError: MethodError: "Method too new to be called from this world context." in Julia

Can someone explain in simple terms why this error occurs and how it can be avoided except not placing the code in main in a function?

Please refer to question Improving the performance of SymPy function generated from string in Julia for the function string_to_func.

Works:

using SymPy

function string_to_func(function_string)
    func_lambdify = lambdify(SymPy.sympify(function_string), invoke_latest=false)
    @eval func(x, y, z) = ($func_lambdify)(x, y, z)
    return Nothing
end

function_string = "x + y + z"
string_to_func(function_string)
result = func(1, 2, 3)

Throws Error:

using SymPy

function string_to_func(function_string)
    expr = lambdify(SymPy.sympify(function_string), invoke_latest=false)
    @eval func(x, y, z) = ($expr)(x, y, z)
    return Nothing
end

function main()
    function_string = "x + y + z"
    string_to_func(function_string)
    result = func(1, 2, 3)
end

main()

Anonymized Error Message:

ERROR: LoadError: MethodError: no method matching func(::Int64, ::Int64, ::Int64)
The applicable method may be too new: running in world age 29676, while current world is 29678.
Closest candidates are:
  func(::Any, ::Any, ::Any) at path_to_folder\test.jl:5 (method too new to be called from this world context.)
Stacktrace:
 [1] main()
   @ Main path_to_folder\test.jl:12
 [2] top-level scope
   @ path_to_folder\test.jl:15
in expression starting at path_to_folder\test.jl:15

Upvotes: 1

Views: 1154

Answers (1)

Simeon Schaub
Simeon Schaub

Reputation: 775

You need to invoke func using Base.invokelatest, i.e.

function main()
    function_string = "x + y + z"
    string_to_func(function_string)
    result = Base.invokelatest(func, 1, 2, 3)
end

See the manual for further details about world age and why invokelatest is needed here.

I should also mention GeneratedFunctions.jl that can avoid some of the overhead associated with invokelatest, although it has it is own caveats since its somewhat of a hack.

Upvotes: 3

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