factor instanceof LocalVariable)){
AbstractArithmetic arithOperator = OperatorFactory.newOperator(Subtraction.class,
new Class<?>[]{ProgramBlock.class, Parameterized.class, Parameterized.class},
block, factor, getValue());
arithOperator.prepare();
MemberVariable mvar = (MemberVariable) factor;
assigner = block.assign(mvar, arithOperator);
assigner.prepare();