Add Repr.is_zero to check if value is small

1 files changed, 5 insertions, 0 deletions

diff --git a/mdpoly/abc.py b/mdpoly/abc.py
index 56507d6..77285aa 100644
--- a/mdpoly/abc.py
+++ b/mdpoly/abc.py
@@ -54,6 +54,7 @@ class Expr(Protocol):
 class Repr(Protocol):
     """
     Representation of a polynomial expression.
+
     """
     @abstractmethod
     def at(self, entry: MatrixIndex, term: PolyIndex) -> Number:
@@ -63,6 +64,10 @@ class Repr(Protocol):
     def set(self, entry: MatrixIndex, term: PolyIndex, value: Number) -> None:
         """ Set value of polynomial entry """
 
+    def is_zero(self, entry: MatrixIndex, term: PolyIndex, eps: Number = NUMERICS_EPS) -> bool:
+        """ Check if a polynomial entry is zero """
+        return self.at(entry, term) < eps
+
     @abstractmethod
     def set_zero(self, entry: MatrixIndex, term: PolyIndex) -> None:
         """ Set an entry to zero """