(-x)^(1//2) gives error in Symbolics.jl

New to Julia
1

I was going to enter an issue for this, but thought to ask first here in case I am not using Julia symbolic correctly as I am still learning it.

>julia
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.8.0 (2022-08-17)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> using Symbolics

julia> @syms x
(x,)

julia> (-x)^(1//2)
ERROR: DomainError with -1.0:
Exponentiation yielding a complex result requires a complex argument.
Replace x^y with (x+0im)^y, Complex(x)^y, or similar.
Stacktrace:
 [1] throw_exp_domainerror(x::Float64)
   @ Base.Math ./math.jl:37
 [2] ^(x::Float64, y::Float64)
   @ Base.Math ./math.jl:1003
 [3] ^
   @ ./promotion.jl:422 [inlined]
 [4] ^
   @ ./rational.jl:481 [inlined]
 [5] unstable_pow
   @ ~/.julia/packages/SymbolicUtils/qulQp/src/types.jl:801 [inlined]
 [6] ^(a::SymbolicUtils.Mul{Number, Int64, Dict{Any, Number}, Nothing}, b::Rational{Int64})
   @ SymbolicUtils ~/.julia/packages/SymbolicUtils/qulQp/src/types.jl:1047
 [7] top-level scope
   @ REPL[3]:1

So how does one write (-x)^(1/2) in Julia, given that x is symbolic?

Note that sqrt(-x) gives no error. But the exponent can be any ratio of two integers and not just 1/2 as in this example. I know I need to use 1//2 and not 1/2 in Julia to make sure it does not convert to 0.5. Any thing I should have done?

2

btw this is not a Julia bug, this is a Symbolics bug, Julia has no built-in symbolic capability; I have changed the title to reflect you’re talking about Symbolics.jl

3

I just noticed this is actually similar to earlier problem I saw. I did not notice the error is same until now.

I already entered a bug report on it. Here is the link.