Create helper PolyDict.is_constant to check if a polynomial is a constant

1 files changed, 14 insertions, 0 deletions

diff --git a/polymatrix/polymatrix/index.py b/polymatrix/polymatrix/index.py
index c906b35..e50df43 100644
--- a/polymatrix/polymatrix/index.py
+++ b/polymatrix/polymatrix/index.py
@@ -161,6 +161,20 @@ class PolyDict(UserDict[MonomialIndex, int | float]):
             return self[MonomialIndex.constant()]
         return 0
 
+    def is_constant(self) -> bool:
+        """
+        Check whether the polynomial is a constant polynomial. 
+        """
+        # polynomial is zero
+        if len(self.keys()) == 0:
+            return True
+
+        if len(self.keys()) > 1:
+            return False
+
+        m, *_ = self.keys()
+        return MonomialIndex.is_constant(m)
+
     def terms(self) -> Iterable[tuple[MonomialIndex, int | float]]:
         """ Iterate over terms with a non-zero coefficient. """
         # This is an alias for readability