real() of complex numbers not working

[jebej]

It seems that conjugation does not work, as it fall back on the conj(x) = x Julia base definition:

julia> @vars a; conj(1im*a)
I*a

[isuruf]

you can define conj(x::Basic) = real(x) - 1im * imag(x) for now

[jebej]

Is this behavior meant to be handled in the C++ code? Is the Basic number type meant to be a real number?

[isuruf]

Is the Basic number type meant to be a real number?

No, it's not. It's just that conj is not defined for Basic yet. (Because nobody needed conj until now)

[jebej]

Ok, but then your definition won't work, since real(1im*a) = I*a currently. It also seems that imag(1im*a) currently throws an error.

[isuruf]

Ah, real and imag are not working properly. This needs to be fixed. One problem is that we don't know whether a is real or not.

[jebej]

Yes, which is why this might need to be handled in the C++ code. In Mathematica, if it is unknown whether a variable is real or not, Real[a] = Real[a]. It basically gets wrapped.

[mikolajpp]

Any progress on this?
I would very much like to have it. Currently doing algebra over complex numbers
is incovenient without this working on more complex types like matrices.

[timziebart]

@isuruf is there a plan for complex number operations to be implemented? I would really like to switch to SymEngine.

[isuruf]

There are no plans yet. Let's figure out what needs to be implemented.

Is it only a Real and Imag class so that conj(a) gives Real(a) + I*Imag(a) as output ?

[timziebart]

Sounds reasonable, but I honestly don't know much about the symengine interface, else I would have submitted a PR already

[GiggleLiu]

There are no plans yet. Let's figure out what needs to be implemented.

Is it only a Real and Imag class so that conj(a) gives Real(a) + I*Imag(a) as output ?

Great tool, really enjoyed playing with SymEngine! Now we need these two classes Imag and Real desperately in YaoSym.jl, otherwise, I need to figure out how to compute the imaginary part of a general sin(x), which is possible, but with a pretty long expression.

[isuruf]

@GiggleLiu, can you describe the functionalities you need from a Real and Imag class?

[GiggleLiu]

It is simple, just “real(sin(x)) -> Re(sin(x))”. Just a function.