/// <param name="e">
/// is the minus expression. </param>
/// <returns> new sub expression </returns>
public virtual object visit(MinusExpr e)
{
e.arg().accept(this);
return(null);
}
/// <param name="e">
/// is the minus expression. </param>
/// <returns> new sub expression </returns>
public virtual object visit(MinusExpr e)
{
SubExpr se = new SubExpr(make_int_lit(0), e.arg());
return(se.accept(this));
}