Deprecate get_var(-1)

Author: jdemeyer

cypari2/gen.pyx

@@ -2374,7 +2374,7 @@ cdef class Gen(Gen_auto):
             R -= 1
         return new_gen(v)
 
-    def Ser(f, v=-1, long precision=-1):
+    def Ser(f, v=None, long precision=-1):
         """
         Return a power series or Laurent series in the variable `v`
         constructed from the object `f`.
@@ -3755,7 +3755,7 @@ cdef class Gen(Gen_auto):
         sig_on()
         return new_gen(eltreltoabs(self.g, t0.g))
 
-    def galoissubfields(self, long flag=0, v=-1):
+    def galoissubfields(self, long flag=0, v=None):
         """
         List all subfields of the Galois group ``self``.
 
@@ -4298,7 +4298,7 @@ cdef class Gen(Gen_auto):
         sig_on()
         return new_gen(factorpadic(self.g, t0.g, r))
 
-    def poldegree(self, var=-1):
+    def poldegree(self, var=None):
         """
         Return the degree of this polynomial.
         """

cypari2/pari_instance.pyx

@@ -1328,7 +1328,7 @@ cdef long get_var(v) except -2:
     Convert ``v`` into a PARI variable number.
 
     If ``v`` is a PARI object, return the variable number of
-    ``variable(v)``. If ``v`` is ``None`` or ``-1``, return -1.
+    ``variable(v)``. If ``v`` is ``None``, return -1.
     Otherwise, treat ``v`` as a string and return the number of
     the variable named ``v``.
 
@@ -1354,6 +1354,8 @@ cdef long get_var(v) except -2:
     2*x
     >>> pari("[Pi,0]").Pol('!@#$%^&')
     3.14159265358979*!@#$%^&
+    >>> pari("[1,0]").Pol(-1)  # Deprecated
+    x
 
     We can use ``varhigher()`` and ``varlower()`` to create
     temporary variables without a name. The ``"xx"`` below is just a
@@ -1383,6 +1385,8 @@ cdef long get_var(v) except -2:
         else:
             return varno
     if v == -1:
+        from warnings import warn
+        warn("using '-1' as variable name is deprecated, use 'None' to mean 'no variable'", DeprecationWarning)
         return -1
     cdef bytes s = to_bytes(v)
     sig_on()