Julia write SymEngine expression to file

Question

When i try to write the expressions from the code to file, i receive an error:

MethodError: no method matching write(::IOStream, ::SymEngine.Basic)

The code i use is considered to write the expressions to file and then take it from there in other programs. Here's my code:

using SymEngine

function Legendre(n)
 @vars x
 a = 1
 Pn = (x^2-1)^n

 for k = (1:n)
     Pn = diff(Pn,x)
     a = a*2*k
        end

       Pn = Pn/a
end

function Asos_Legendre(n,s)
 @vars x
 Pn=Legendre(n)
        for l = (1:s)
            Pn = diff(Pn,x)
        end
        a = (1-x^2)^(s/2)*(-1)^(s)
        Pn = Pn*a

end

function Asos_Legendre_diff(n,s)
 @vars x
        Pn=Asos_Legendre(n,s)
        Pn1 = diff(Pn,x)
        d = (1-x^2)^(s/2)*(-1)^s
        b = x*(-1)^(s+1)*s*(1-x^2)^(s/2-1)
        a = Pn1*d + Pn*b

    open("C:/stj/Julia/test3.txt", "w") do f
            write(f,)
        end
end

Maybe there is a way to convert SymEngine.Basic objects to String and inverse? I could write them as a String and then convert them back into SymEngine then.

Answer 1

Do ex = convert(Expr,b) to change the SymEngine.Basic into an Expr. From there, you can convert(String,ex), or if you attempt to do things like write it to a file then it will automatically convert to a string.