I am trying to get the coefficients from several SymPy expressions. Since there are a lot of different combinations, I’d like to loop over them with a variable `n`

. However that fails when `n=-1`

. Here is an example, where the first two attempts are explicit and work fine, and the last with the exponent written as a variable fails:

```
julia> using SymPy
julia> @syms x
(x,)
julia> p = 1/x
1
─
x
julia> p.coeff(1/x) # Yay, this works!
1
julia> p.coeff(x^(-1)) # This also works!
1
julia> n = -1; p.coeff(x^n) # Crash, bang, catastrophy.
ERROR: DomainError with -1:
Cannot raise an integer x to a negative power -1.
Convert input to float.
Stacktrace:
[1] throw_domerr_powbysq(#unused#::Sym, p::Int64)
@ Base ./intfuncs.jl:241
[2] power_by_squaring(x_::Sym, p::Int64)
@ Base ./intfuncs.jl:265
[3] ^(x::Sym, p::Int64)
@ Base ./intfuncs.jl:290
[4] top-level scope
@ REPL[6]:1
```

To me this smells like some compiler inference stuff… meaning I have no clue what I’m talking about. Even just an explanation of what is going on would be greatly appreciated!