Extend ideal interface

src/Ideal.jl

@@ -4,17 +4,33 @@
 #
 ###############################################################################
 
-function ideal
-end
+# We assume that the functions
+#   ideal(R::Ring, x::RingElement)
+#   ideal(R::Ring, xs::AbstractVector)
+# are implemented by anyone implementing ideals for AbstractAlgebra rings.
+# The functions in this file extend the interface for `ideal`.
 
-function *(x::RingElement, R::Ring)
+function *(R::Ring, x::Any)
   return ideal(R, x)
 end
 
-function *(R::Ring, x::RingElement)
+function *(x::Any, R::Ring)
   return ideal(R, x)
 end
 
+function ideal(R::Ring, x::Any)
+  return ideal(R, R(x))
+end
+
+function ideal(x::RingElement)
+  return ideal(parent(x), x)
+end
+
+function ideal(xs::AbstractVector{T}) where T<:RingElement
+  !is_empty(xs) || throw(ArgumentError("Empty collection, cannot determine parent ring, try ideal(ring, xs) instead of ideal(xs)"))
+  return ideal(parent(xs[1]), xs)
+end
+
 iszero(I::Ideal) = all(iszero, gens(I))
 
 base_ring_type(::Type{<:IdealSet{T}}) where T <: RingElement = parent_type(T)