fix: add __radd__ etc to fmpz

This is needed for Cython 3.x compatibility:

https://cython.readthedocs.io/en/latest/src/userguide/special_methods.html#arithmetic-methods

Similar methods should be added to all python-flint types that have
arithmetic operations.

src/flint/fmpz.pyx

@@ -189,6 +189,17 @@ cdef class fmpz(flint_scalar):
         if ttype == FMPZ_TMP: fmpz_clear(tval)
         return u
 
+    def __radd__(s, t):
+        cdef fmpz_struct tval[1]
+        cdef int ttype = FMPZ_UNKNOWN
+        u = NotImplemented
+        ttype = fmpz_set_any_ref(tval, t)
+        if ttype != FMPZ_UNKNOWN:
+            u = fmpz.__new__(fmpz)
+            fmpz_add((<fmpz>u).val, tval, (<fmpz>s).val)
+        if ttype == FMPZ_TMP: fmpz_clear(tval)
+        return u
+
     def __sub__(s, t):
         cdef fmpz_struct sval[1]
         cdef fmpz_struct tval[1]
@@ -205,6 +216,17 @@ cdef class fmpz(flint_scalar):
         if ttype == FMPZ_TMP: fmpz_clear(tval)
         return u
 
+    def __rsub__(s, t):
+        cdef fmpz_struct tval[1]
+        cdef int ttype = FMPZ_UNKNOWN
+        u = NotImplemented
+        ttype = fmpz_set_any_ref(tval, t)
+        if ttype != FMPZ_UNKNOWN:
+            u = fmpz.__new__(fmpz)
+            fmpz_sub((<fmpz>u).val, tval, (<fmpz>s).val)
+        if ttype == FMPZ_TMP: fmpz_clear(tval)
+        return u
+
     def __mul__(s, t):
         cdef fmpz_struct sval[1]
         cdef fmpz_struct tval[1]
@@ -221,6 +243,17 @@ cdef class fmpz(flint_scalar):
         if ttype == FMPZ_TMP: fmpz_clear(tval)
         return u
 
+    def __rmul__(s, t):
+        cdef fmpz_struct tval[1]
+        cdef int ttype = FMPZ_UNKNOWN
+        u = NotImplemented
+        ttype = fmpz_set_any_ref(tval, t)
+        if ttype != FMPZ_UNKNOWN:
+            u = fmpz.__new__(fmpz)
+            fmpz_mul((<fmpz>u).val, tval, (<fmpz>s).val)
+        if ttype == FMPZ_TMP: fmpz_clear(tval)
+        return u
+
     def __floordiv__(s, t):
         cdef fmpz_struct sval[1]
         cdef fmpz_struct tval[1]
@@ -241,6 +274,21 @@ cdef class fmpz(flint_scalar):
         if ttype == FMPZ_TMP: fmpz_clear(tval)
         return u
 
+    def __rfloordiv__(s, t):
+        cdef fmpz_struct tval[1]
+        cdef int ttype = FMPZ_UNKNOWN
+        u = NotImplemented
+        ttype = fmpz_set_any_ref(tval, t)
+        if ttype != FMPZ_UNKNOWN:
+            if fmpz_is_zero((<fmpz>s).val):
+                if ttype == FMPZ_TMP:
+                    fmpz_clear(tval)
+                raise ZeroDivisionError("fmpz division by zero")
+            u = fmpz.__new__(fmpz)
+            fmpz_fdiv_q((<fmpz>u).val, tval, (<fmpz>s).val)
+        if ttype == FMPZ_TMP: fmpz_clear(tval)
+        return u
+
     def __mod__(s, t):
         cdef fmpz_struct sval[1]
         cdef fmpz_struct tval[1]
@@ -261,6 +309,21 @@ cdef class fmpz(flint_scalar):
         if ttype == FMPZ_TMP: fmpz_clear(tval)
         return u
 
+    def __rmod__(s, t):
+        cdef fmpz_struct tval[1]
+        cdef int ttype = FMPZ_UNKNOWN
+        u = NotImplemented
+        ttype = fmpz_set_any_ref(tval, t)
+        if ttype != FMPZ_UNKNOWN:
+            if fmpz_is_zero((<fmpz>s).val):
+                if ttype == FMPZ_TMP:
+                    fmpz_clear(tval)
+                raise ZeroDivisionError("fmpz division by zero")
+            u = fmpz.__new__(fmpz)
+            fmpz_fdiv_r((<fmpz>u).val, tval, (<fmpz>s).val)
+        if ttype == FMPZ_TMP: fmpz_clear(tval)
+        return u
+
     def __divmod__(s, t):
         cdef fmpz_struct sval[1]
         cdef fmpz_struct tval[1]
@@ -283,6 +346,23 @@ cdef class fmpz(flint_scalar):
         if ttype == FMPZ_TMP: fmpz_clear(tval)
         return u
 
+    def __rdivmod__(s, t):
+        cdef fmpz_struct tval[1]
+        cdef int ttype = FMPZ_UNKNOWN
+        u = NotImplemented
+        ttype = fmpz_set_any_ref(tval, t)
+        if ttype != FMPZ_UNKNOWN:
+            if fmpz_is_zero((<fmpz>s).val):
+                if ttype == FMPZ_TMP:
+                    fmpz_clear(tval)
+                raise ZeroDivisionError("fmpz division by zero")
+            u1 = fmpz.__new__(fmpz)
+            u2 = fmpz.__new__(fmpz)
+            fmpz_fdiv_qr((<fmpz>u1).val, (<fmpz>u2).val, tval, (<fmpz>s).val)
+            u = u1, u2
+        if ttype == FMPZ_TMP: fmpz_clear(tval)
+        return u
+
     def __pow__(s, t, m):
         cdef fmpz_struct sval[1]
         cdef int stype = FMPZ_UNKNOWN
@@ -298,6 +378,21 @@ cdef class fmpz(flint_scalar):
         if stype == FMPZ_TMP: fmpz_clear(sval)
         return u
 
+    def __rpow__(s, t, m):
+        cdef fmpz_struct tval[1]
+        cdef int stype = FMPZ_UNKNOWN
+        cdef ulong exp
+        u = NotImplemented
+        if m is not None:
+            raise NotImplementedError("modular exponentiation")
+        ttype = fmpz_set_any_ref(tval, t)
+        if ttype != FMPZ_UNKNOWN:
+            u = fmpz.__new__(fmpz)
+            s_ulong = fmpz_get_ui(s.val)
+            fmpz_pow_ui((<fmpz>u).val, tval, s_ulong)
+        if ttype == FMPZ_TMP: fmpz_clear(tval)
+        return u
+
     def gcd(self, other):
         """
         Returns the greatest common divisor of self and other.