Hi, I noticed that the function generated by eval is always a global function , making the code silly if I would like to generate some function defined in string. Are there any other ways to do something like this while avoid using eval? Examples are: function foo() return eval(parse("x->x")) e…

No more than the two I described in the linked discussion.

Use eval to define foo not in the body of foo: julia> @eval foo() = $(Meta.parse("x->x")) foo (generic function with 1 method) julia> foo() #5 (generic function with 1 method) julia> foo()(1) 1

Are you entirely certain you actually need to be defining functions by parsing strings? This can certainly be done, but it’s a design that can lead to fragile code, security vulnerabilities, and/or performance issues. Can you describe the actual problem you’re trying to solve?

FWIW, there’s a hack that allows you to define functions from expressions at runtime, without world age issues: julia> funs = [] 0-element Array{Any,1} julia> @generated make_fun(::Val{N}, x) where N = funs[N] make_fun (generic function with 3 methods) julia> evil(code) = (push!(funs, code); x->m…

invokelatest and other hacks are only necessary if you’re calling code from something that’s long-running and can’t get recompiled and called afresh later when you (re)define foo. For example, the REPL itself. If you define foo() using eval and then call foo() later it will work fine without any add…

My solution to this problem is implemented in the SyntaxTree package (on the most recent master branch) julia> using SyntaxTree julia> SyntaxTree.genfun(:(x^2+1),[:x]) (::#1) (generic function with 1 method) julia> ans(2) 5 This automatically handles the Base.invokelatest action for you, so all …

Well, I am working with SymPy. I would like to build a symbolic matrix and then numerically calculate it. However I found SymPy cannot do the calculation fast enough, e.g. using SymPy @vars x expr=integrate(sin(x)) f=eval(parse("x->$(repr(expr))")) g=lambdify(expr,[x]) @time subs(expr,x=>1.0) @…

Have you tried using [image] GitHub - chakravala/Reduce.jl: Symbolic parser for Julia language term... Symbolic parser for Julia language term rewriting using REDUCE algebra - GitHub - chakravala/Reduce.jl: Symbolic parser for Julia language term rewriting using REDUCE algebra …

Generate functions inside a function from string

General Usage Performance

GunnarFarneback July 12, 2018, 1:24pm 2

Topic		Replies	Views
How do I create a function from an expression General Usage question	23	4764	July 13, 2018
Evaluating a SyntaxTree.genfun within a function Specific Domains package , metaprogramming	6	644	September 23, 2020
Can you avoid using Base.invokelatest in this example? General Usage	20	2738	January 13, 2020
Parsing expressions into functions Performance	22	2170	June 11, 2019
Codegen woes Performance	30	2518	August 27, 2019

Generate functions inside a function from string

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