Some fixes and a minor tweak (#1885)

- Better conversion to CalciumField / zzModPolyRing
- Fix neg! for FpFieldElem
- Fix neg! for ZZModRingElem
- Fix one! for ZZModRingElem

src/calcium/ca.jl

@@ -1470,6 +1470,10 @@ function (C::CalciumField)(v::QQBarFieldElem)
   return z
 end
 
+function (C::CalciumField)(v::RationalUnion)
+  return C(flintify(v))
+end
+
 # todo: optimize
 function (C::CalciumField)(v::Complex{Int})
   return C(QQBarFieldElem(v))

src/flint/FlintTypes.jl

@@ -615,13 +615,8 @@ mutable struct zzModPolyRingElem <: PolyRingElem{zzModRingElem}
     return z
   end
 
-  function zzModPolyRingElem(n::UInt, a::Int)
-    z = new()
-    ccall((:nmod_poly_init, libflint), Nothing, (Ref{zzModPolyRingElem}, UInt), z, n)
-    ccall((:nmod_poly_set_coeff_ui, libflint), Nothing,
-          (Ref{zzModPolyRingElem}, Int, UInt), z, 0, mod(a, n))
-    finalizer(_nmod_poly_clear_fn, z)
-    return z
+  function zzModPolyRingElem(n::UInt, a::Integer)
+    return zzModPolyRingElem(n, mod(a, n) % UInt)
   end
 
   function zzModPolyRingElem(n::UInt, arr::Vector{ZZRingElem})

src/flint/fmpz_mod.jl

@@ -343,15 +343,21 @@ function zero!(z::ZZModRingElem)
 end
 
 function one!(z::ZZModRingElem)
-  one!(z.data)
+  R = parent(z)
+  if R.n == 1
+    zero!(z.data)
+  else
+    one!(z.data)
+  end
   return z
 end
 
-function neg!(z::ZZModRingElem, a::ZZModRingElem)
-  if iszero(a.data)
-    z.data = zero!(z.data)
+function neg!(z::ZZModRingElem, x::ZZModRingElem)
+  R = parent(z)
+  if is_zero(x.data)
+    zero!(z.data)
   else
-    z.data = sub!(z.data, R.n, a.data)
+    sub!(z.data, R.n, x.data)
   end
   return z
 end

src/flint/gfp_fmpz_elem.jl

@@ -360,7 +360,12 @@ function one!(z::FpFieldElem)
 end
 
 function neg!(z::FpFieldElem, x::FpFieldElem)
-  z.data = R.n - x.data
+  R = parent(z)
+  if is_zero(x.data)
+    zero!(z.data)
+  else
+    sub!(z.data, R.n, x.data)
+  end
   return z
 end