Fix issue #724 with binomialIsPrime not working right.

M2/Macaulay2/packages/Binomials.m2

@@ -23,8 +23,8 @@
 
 newPackage(
 	"Binomials",
-	Version => "1.2",
-	Date => "April 2015",
+	Version => "1.2.1",
+	Date => "January 2018",
 	Authors => {{
 		  Name => "Thomas Kahle",
 		  Email => "thomas.kahle@jpberlin.de",
@@ -629,6 +629,11 @@ binomialIsPrime Ideal := Ideal => o -> I -> (
      	  if cv === false  then return false)
      else cv = o#CellVariables;
 
+     -- Check if non-cellular variables are all contained:
+     R := ring I;
+     ncv := toList(set (gens R) - cv); -- nilpotent variables x \notin E
+     if not isSubset(promote(ideal ncv, R), I) then return false;
+
      -- Test if the partial character saturated:
      pc := partialCharacter (I, CellVariables=>cv);
      if image Lsat pc#"L" != image pc#"L" then return false;
@@ -1976,6 +1981,13 @@ for L in permutations {I1,I2,I3} do (
     )
 ///
 
+TEST ///
+R = QQ[x,y]
+assert(binomialIsPrime ideal x^2 == false)
+assert(binomialIsPrime ideal (x^2-y^2) == false)
+assert(binomialIsPrime ideal (x-y) == true)
+///
+
 end
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 restart