Add some convert method to/from QQBarFieldElem

src/calcium/qqbar.jl

@@ -1414,6 +1414,17 @@ function (::Type{Float64})(a::QQBarFieldElem)
   return Float64(x)
 end
 
+function (::Type{T})(a::QQBarFieldElem) where {T <: Integer}
+  return T(ZZRingElem(a))
+end
+
+function (::Type{T})(a::QQBarFieldElem) where {T <: Rational}
+  return T(QQFieldElem(a))
+end
+
+convert(::Type{QQBarFieldElem}, a::RationalUnion) = QQBarFieldElem(a)
+convert(::Type{T}, a::QQBarFieldElem) where {T <: RationalUnion} = T(a)
+
 ###############################################################################
 #
 #   Unsafe functions

test/calcium/qqbar-test.jl

@@ -418,4 +418,35 @@ end
   x = sqrt(R(-2))
   @test_throws InexactError Float64(x)
   @test isapprox(ComplexF64(x),sqrt(complex(-2)))
+
+
+  x = R(2)
+  for T in [Int16, UInt32, Int, BigInt, Rational{Int}, Rational{BigInt}, ZZRingElem, QQFieldElem]
+    y = convert(T, x)
+    @test y::T == 2
+
+    y = T(x)
+    @test y::T == 2
+
+    z = convert(QQBarFieldElem, y)
+    @test z::QQBarFieldElem == x
+
+    z = QQBarFieldElem(y)
+    @test z::QQBarFieldElem == x
+  end
+
+  x = R(2//3)
+  for T in [Rational{Int}, Rational{BigInt}, QQFieldElem]
+    y = convert(T, x)
+    @test y::T == 2//3
+
+    y = T(x)
+    @test y::T == 2//3
+
+    z = convert(QQBarFieldElem, y)
+    @test z::QQBarFieldElem == x
+
+    z = QQBarFieldElem(y)
+    @test z::QQBarFieldElem == x
+  end
 end