3 files changed, 42 insertions, 2 deletions
diff --git a/src/base/main/main.h b/src/base/main/main.h
index 6fc2c356..7f2d11bf 100644
--- a/src/base/main/main.h
+++ b/src/base/main/main.h
@@ -133,11 +133,10 @@ extern ABC_DLL void            Abc_FrameSetCex( Abc_Cex_t * pCex );
 extern ABC_DLL void            Abc_FrameSetNFrames( int nFrames );
 extern ABC_DLL void            Abc_FrameSetStatus( int Status );
 
+extern ABC_DLL int             Abc_FrameCheckPoConst( Abc_Frame_t * p, int iPoNum );
 
 ABC_NAMESPACE_HEADER_END
 
-
-
 #endif
 
 ////////////////////////////////////////////////////////////////////////
diff --git a/src/base/main/mainFrame.c b/src/base/main/mainFrame.c
index df1b385e..8c3344ff 100644
--- a/src/base/main/mainFrame.c
+++ b/src/base/main/mainFrame.c
@@ -648,6 +648,40 @@ void Abc_FrameSetSave2( void * pAig )
 void * Abc_FrameReadSave1()  { void * pAig = Abc_FrameGetGlobalFrame()->pSave1; Abc_FrameGetGlobalFrame()->pSave1 = NULL; return pAig; }
 void * Abc_FrameReadSave2()  { void * pAig = Abc_FrameGetGlobalFrame()->pSave2; Abc_FrameGetGlobalFrame()->pSave2 = NULL; return pAig; }
 
+/**Function*************************************************************
+
+  Synopsis    [Returns 0/1 if pNtkCur is an AIG and PO is 0/1; -1 otherwise.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_FrameCheckPoConst( Abc_Frame_t * p, int iPoNum )
+{
+    Abc_Obj_t * pObj;
+    if ( p->pNtkCur == NULL )
+        return -1;
+    if ( !Abc_NtkIsStrash(p->pNtkCur) )
+        return -1;
+    if ( iPoNum < 0 || iPoNum >= Abc_NtkPoNum(p->pNtkCur) )
+        return -1;
+    pObj = Abc_NtkPo( p->pNtkCur, iPoNum );
+    if ( !Abc_AigNodeIsConst(Abc_ObjFanin0(pObj)) )
+        return -1;
+    return !Abc_ObjFaninC0(pObj);
+}
+void Abc_FrameCheckPoConstTest( Abc_Frame_t * p )
+{
+    Abc_Obj_t * pObj;
+    int i;
+    Abc_NtkForEachPo( p->pNtkCur, pObj, i )
+        printf( "%d = %d\n", i, Abc_FrameCheckPoConst(p, i) );
+}
+
+
 ////////////////////////////////////////////////////////////////////////
 ///                       END OF FILE                                ///
 ////////////////////////////////////////////////////////////////////////
diff --git a/src/python/pyabc.i b/src/python/pyabc.i
index bb8cc3ca..01d14379 100644
--- a/src/python/pyabc.i
+++ b/src/python/pyabc.i
@@ -195,6 +195,12 @@ int n_phases()
     return pNtk ? Abc_NtkPhaseFrameNum(pNtk) : 1;
 }
 
+int is_const_po( int iPoNum )
+{
+    Abc_Frame_t* pAbc = Abc_FrameGetGlobalFrame();
+    return Abc_FrameCheckPoConst( pAbc, iPoNum );
+}
+
 Abc_Cex_t* _cex_get()
 {
     Abc_Frame_t* pAbc = Abc_FrameGetGlobalFrame();
@@ -626,6 +632,7 @@ int  cex_po();
 int  cex_frame();
 
 int  n_phases();
+int  is_const_po( int iPoNum );
 
 Abc_Cex_t* _cex_get();
 int _cex_get_vec_len();