declared and installed PrimaryIdealOfGrAnnOfPowerAtTheOrigin

PackageInfo.g

@@ -27,7 +27,7 @@ Subtitle := "A homalg based package for D-modules",
 ##  See '?Extending: Version Numbers' in GAP help for an explanation
 ##  of valid version numbers. For an automatic package distribution update
 ##  you must provide a new version number even after small changes.
-Version := "2015.02.25",
+Version := "2015.02.26",
 ##  Please adjust also the VERSION file in the package directory when
 ##  changing this.
 

gap/D-Modules.gd

@@ -85,9 +85,11 @@ DeclareOperation( "OrderOfFirstEquality",
 DeclareOperation( "FiltrationByOrder",
         [ IsInt, IsHomalgModule ] );
 
+DeclareOperation( "PrimaryIdealOfGrAnnOfPowerAtTheOrigin",
+        [ IsInt, IsDivisor ] );
+
 ####################################
 #
 # synonyms:
 #
 ####################################
-

gap/D-Modules.gi

@@ -462,3 +462,35 @@ InstallMethod( FiltrationByOrder,
     return HomalgAscendingFiltration( filt );
 
 end );
+
+##
+InstallMethod( PrimaryIdealOfGrAnnOfPowerAtTheOrigin,
+        "for a homalg divisor",
+        [ IsInt, IsDivisorRep ],
+
+  function( s, D )
+    local anns, granns, R, m, pr;
+
+    anns := AnnihilatorOfPower( s, D );
+
+    granns := AssociatedOrderGradedModule( anns );
+
+    R := HomalgRing( granns );
+
+    m := Indeterminates( BaseRing( R ) );
+    m := LeftSubmodule( m );
+    m := R * m;
+
+    pr := PrimaryDecomposition( granns );
+
+    pr := First( pr, a -> a[2] = m );
+
+    if pr = fail then
+        return m^0;
+    fi;
+
+    SetAssociatedPrimes( pr[1], [ pr[2] ] );
+
+    return pr[1];
+
+end );