Kaz Kylheku wrote: > The removal for the need for manual object lifetime computation does > not cause a whole class of useful programs to be rejected.
Sometimes you must be able to guarantee that a resource has been disposed before you can continue. That is why we have finalisers in OCaml and dispose in .NET (to manage external resources). > In fact, all previously correct programs continue to work as before, Removing (external) resource allocation will break some programs. > and in addition, some hitherto incorrect programs become correct. > That's an increase in power: new programs are possible without losing > the old ones. It is a trade-off. Aside from managing external resources, GC has performance implications that affect the design decisions of real-time applications. > Wheas programs can't be made to conform to the pure functional paradigm > by adjusting the semantics of some API function. Programs which don't > conform have to be rejected, You can rephrase any impure program as a pure program (Turing). >> Reliable GC gets rid of a large and >> important class of program errors and makes possible programming in a >> style that relies on it. > > Right. GC gets rid of /program errors/. Pure functional programming > gets rid of /programs/. Pure functional programming does not get rid of any programs. Pure functional programming does get rid of program errors, e.g. concurrency issues. >> You can make languages more powerful by removing features as well as by >> adding them. > > Note that changing the storage liberation request from an imperative to > a hint isn't the removal of a feature. It's the /addition/ of a > feature. The new feature is that objects can still be reliably used > after the implementation was advised by the program that they are no > longer needed. Programs which do this are no longer buggy. Another new > feature is that programs can fail to advise the implementation that > some objects are no longer needed, without causing a leak, so these > programs are no longer buggy. The pool of non-buggy programs has > increased without anything being rejected. You have rejected all programs that rely upon a resource being disposed before a certain point. -- Dr Jon D Harrop, Flying Frog Consultancy Objective CAML for Scientists http://www.ffconsultancy.com/products/ocaml_for_scientists/index.html?usenet -- http://mail.python.org/mailman/listinfo/python-list
