Hello,

I’m working on a piece of code that generates a math expression with embedded variables, and I want to generate a function that will take those variables as inputs and evaluate the math expression using the given inputs. E.g., if my math expression ends up being `a + b`

, I want to have a generated function that takes `a`

and `b`

as inputs and will evaluate `a + b`

. The purpose of this is that generating my math expression takes a lot of time, but once I have the math expression, evaluating it should be fast, and I want to be able to evaluate it with different variables a large number of times.

My thinking was to use a nested function approach where the variable names and final math expression are interpolated into an inner function definition, which hopefully I can later call to evaluate the equation. Here’s a contrived example of what I’m trying to do where the math expression is just a sum of `num`

variables:

```
function make_func(num::Int)
# Generate some variables
vars = String[]
for i = 1:num
push!(vars, "v"*string(i))
end
# Generate an equation using these variables
my_sum = ""
for var in vars
my_sum = my_sum * var * " + "
end
my_sum = my_sum[1:end-3]
# Create a function that will evaluate this equation
@eval begin
function new_func(vars...)
the_sum = Meta.parse($my_sum)
return the_sum
end
end
end
```

Ideally, running `make_func(3)`

would generate a function called `new_func`

which takes 3 inputs, calculates the sum of the values, and returns the sum. But this doesn’t work:

```
julia> make_func(3); new_func(1,5,7)
:(v1 + v2 + v3)
julia> new_func()
:(v1 + v2 + v3)
```

For one thing, `new_func(vars...)`

is clearly not creating a function where the elements of “vars” are the arguments. And for another thing, the `:(v1 + v2 + v3)`

expression seems to be detached from the inputs to `new_func`

, which means I can’t get its evaluation.

Is there any way to do something like this? Some fix to the nested function? A way to evaluate a code-generated expression multiple times without re-generating it?

Any help would be greatly appreciated!

Thanks!