Singular

system("reference");
  system("shared");


proc computeImage( parentRingRef, childRingRef,  srcIdealName, dstIdealName )
{
    def refRing = basering;

    def localChildRing = link(childRingRef);
    def localParentRing = link(parentRingRef);
    setring localChildRing;

    string mapCmd = "def " + dstIdealName + " = phi("+srcIdealName+");";
    execute(mapCmd);   

    string exportCmd = "export( "+dstIdealName+");";
    execute( exportCmd );   

    setring refRing;
    kill localChildRing;
    kill localParentRing;
    return (0);
}


proc computePreimage (parentRingRef,childRingRef, srcIdealName, dstIdealName)
{
    def localParentRing = link  (parentRingRef);
    def localChildRing = link  (childRingRef);
    def refRing = basering;

    setring localParentRing;
   
    string mapCmd = "def " + dstIdealName + " =  preimage( localChildRing, phi, " + srcIdealName + ");";       
    execute( mapCmd );   

    string exportCmd = "export( " + dstIdealName + " );";
    execute( exportCmd );   


    setring refRing;
    kill localChildRing;
    kill localParentRing;
    return ( 0 );
}



proc testPreimage1()
{
    ring parentRing = integer,(x,y,z),dp;
    reference parentRingRef = parentRing;
   
    ideal I = x^3+y;

    ring childRing = integer,(X(1),X(2)),dp;
    reference childRingRef = childRing;

    setring    childRing;

    ideal cX = X(1)^3+X(2);

    ideal mapIdeal = X(1),X(2);
    export(mapIdeal);
    map phi = parentRing, mapIdeal;
    export(phi);
 

    computeImage(parentRingRef, childRingRef, "I", "mappedI");

    computePreimage(parentRingRef, childRingRef, "cX", "pX");
}


// fails:
testPreimage1();

system("reference");

proc setAttrib( rng, attrubuteName, attributeVal)
{
   attrib( rng, attrubuteName, attributeVal);
}

proc setAttribOfRef( pRngRef, attrubuteName, attributeVal)
{
   attrib( pRngRef ,attrubuteName, attributeVal);
}


proc minimalExample()
{
   string attributeName = "name";
   string attributeVal  = "it works!";

   ring parentRing = integer,(x,y,z),dp;
   
   setAttrib( parentRing,attributeName,attributeVal);
   if ( attrib( parentRing, attributeName )<> attributeVal ) 
   { print("setting attrubute by passing ordinary copy failed"); }
   else   { print("setting attrubute by passing ordinary copy succeeded"); }

   reference rngRef =  parentRing;

   setAttribOfRef(  rngRef,attributeName,attributeVal);
   if ( attrib( parentRing, attributeName )<> attributeVal ) 
   { print("setting attrubute by passing reference failed"); }
   else  { print("setting attrubute by passing reference succeeded !"); }
}


minimalExample();