 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Java Forum / General / February 2006Lisp-style list
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 NotDashEscaped: You need GnuPG to verify this message Hi, I want a list in which I can add at any place, but whose size is not statically known. So after creating, if I do get(i) for an i for which there is no value yet, I?d just get null, and if I do add(i, element) when for some value < i no value is present yet, these values would just all be null. Is there something like this, or will I have to do it the hard way with an ArrayList? Thanks, H.  SignatureHendrik Maryns ================== www.lieverleven.be http://aouw.org > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 [quoted text clipped - 10 lines] > > Thanks, H. It sounds to me like ArrayList is the easy way. Lisp lists dont directly support most of what you want, functions do. Its easy enough to write a simple class implementing a cons cell with a next pointer, and add whatever 'lisp' methods to that, but if all you need is a list, go with the provided ones. > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 [quoted text clipped - 8 lines] > all be null. Is there something like this, or will I have to do it the > hard way with an ArrayList? AFAIK you'll have to do it your own - unless you find a lib out there that does it. However, you can inherit AbstractList and get a lot methods for free. Alternatively you could use a map with int as index, but unless you are on 1.5 you'll have to do the boxing yourself. Note also, that boxing of primitive values has some performance implications depending on your application. Kind regards robert >I want a list in which I can add at any place, but whose size is not >statically known. So after creating, if I do get(i) for an i for which >there is no value yet, I?d just get null, and if I do add(i, element) This has nothing to do with Lisp. Something similar is called a "sparse array". You could use a Map implementation in Java for this purpose, for example, "java.util.HashMap". I you really need Lisp, there are Java-libraries for it, like »Jatha«. A Lisp list is easily done: private final int car; private final List cdr; List( final int car, final List cdr ){ this.car = car; this.cdr = cdr; } But this is not what you asked for. On Tue, 21 Feb 2006 11:35:35 +0100, Hendrik Maryns <hendrik_maryns@despammed.com> wrote, quoted or indirectly quoted someone who said : >I want a list in which I can add at any place, but whose size is not >statically known. So after creating, if I do get(i) for an i for which >there is no value yet, I?d just get null, and if I do add(i, element) >when for some value < i no value is present yet, these values would just >all be null. Is there something like this, or will I have to do it the >hard way with an ArrayList? see http://mindprod.com/jgloss/arraylist.html#GROWINGARRAYLIST SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 NotDashEscaped: You need GnuPG to verify this message Roedy Green schreef: > On Tue, 21 Feb 2006 11:35:35 +0100, Hendrik Maryns > <hendrik_maryns@despammed.com> wrote, quoted or indirectly quoted [quoted text clipped - 8 lines] > > see http://mindprod.com/jgloss/arraylist.html#GROWINGARRAYLIST Thanks Roedy, that is exactly what I need, with some more methods like this for get and add, but I can add them myself. I looked at the page before, but have read over it. H. SignatureHendrik Maryns ================== www.lieverleven.be http://aouw.org On Wed, 22 Feb 2006 11:04:04 +0100, Hendrik Maryns <hendrik_maryns@despammed.com> wrote, quoted or indirectly quoted someone who said : >Thanks Roedy, that is exactly what I need, with some more methods like >this for get and add, but I can add them myself. I looked at the page >before, but have read over it. Inherited get is ok, unless you want it to grow the array rather than throw a subscript out of range. inherited add should do fine. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. On Tue, 21 Feb 2006 11:35:35 +0100, Hendrik Maryns <hendrik_maryns@despammed.com> wrote, quoted or indirectly quoted someone who said : >I want a list in which I can add at any place, but whose size is not >statically known. So after creating, if I do get(i) for an i for which >there is no value yet, I?d just get null, and if I do add(i, element) >when for some value < i no value is present yet, these values would just >all be null. Is there something like this, or will I have to do it the >hard way with an ArrayList? see also http://mindprod.com/products1.html#LINKEDLIST I wrote it for Java 1.0. It is implemented as a chain of objects, no backing array like Sun's later version. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 NotDashEscaped: You need GnuPG to verify this message Roedy Green schreef: > On Tue, 21 Feb 2006 11:35:35 +0100, Hendrik Maryns > <hendrik_maryns@despammed.com> wrote, quoted or indirectly quoted [quoted text clipped - 11 lines] > I wrote it for Java 1.0. It is implemented as a chain of objects, no > backing array like Sun's later version. You must have meant http://mindprod.com/jgloss/linkedlist.html. H. SignatureHendrik Maryns ================== www.lieverleven.be http://aouw.org On Wed, 22 Feb 2006 11:05:22 +0100, Hendrik Maryns <hendrik_maryns@despammed.com> wrote, quoted or indirectly quoted someone who said : >> see also http://mindprod.com/products1.html#LINKEDLIST >> >> I wrote it for Java 1.0. It is implemented as a chain of objects, no >> backing array like Sun's later version. > >You must have meant http://mindprod.com/jgloss/linkedlist.html. I meant http://mindprod.com/products2.html#LINKEDLIST which the page you found links to. That is the download. I moved it to the second string section. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
|
Reply to this Message
|
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.