More friendly Equation printing

Author: YingboMa

src/equations.jl

@@ -14,6 +14,7 @@ struct Equation
 end
 Base.:(==)(a::Equation, b::Equation) = all(isequal.((a.lhs, a.rhs), (b.lhs, b.rhs)))
 Base.hash(a::Equation, salt::UInt) = hash(a.lhs, hash(a.rhs, salt))
+Base.show(io::IO, eq::Equation) = print(io, eq.lhs, " ~ ", eq.rhs)
 
 SymbolicUtils.simplify(x::Equation; kw...) = simplify(x.lhs; kw...) ~ simplify(x.rhs; kw...)