Hi Igor, Thank you very much for your thorough reply. May be I did not express myself properly, but I am not really interested in discussing the implementation of a Matrix. It was only an example. I'm interested in discussing wether or not people in the community find it neat and useful to have a method that behaves like #collect: but without arguments, just like #timesRepeat: for the iterations. Sorry for the misunderstanding. Cheers r. -----Original Message----- From: pharo-project-bounces@lists.gforge.inria.fr [mailto:pharo-project-bounces@lists.gforge.inria.fr] On Behalf Of Igor Stasenko Sent: 20 May 2009 09:40 To: Pharo-project@lists.gforge.inria.fr Subject: Re: [Pharo-project] Smalltalk idiom 2009/5/20 Ramiro Diaz Trepat <ramiro@diaztrepat.name>:
I have a simple question regarding the use of a proper idiom. I had to create a matrix (n X m) of random values and I used a line similar to this one: NMatrix withRows: ((1 to: n) collect: [ :i | random next: m ]).
Since Smalltalk is so neat for its collection handling, I obviously did not like to write that line. I thought that I did not want to explicitly create the interval, nor use a block that requires an argument that I also don't use. The question, finally, is if there an elegant way of replicating the behaviour of #collect: but without the argument? In my case, I thought it would be great for Integer to have something like #timesCollect: that would allow me to rewrite the line above as: NMatrix withRows: (n timesCollect: [ random next: m ]) Does anyone else think that this would be an useful method to have?
depends on how you represent a matrix. It seems that you using a collection of N rows. IMO its more efficient to use a flat array, while you can declare the matrix as: Array subclass: #NMatrix instanceVariables: 'numRows' then, an instance size \\ numRows - gives number of columns and you can simply add/override some methods , while reuse most of Collection protocol when you don't need to care about item row/col position - like in regular flat Array. Override a #species method, so NMatrix collect: will create NMatrix when using #collect: and other related methods. Then, a multiplication can be implemented as: NMatrix >>* numberOrMatrix ^ numberOrMatrix isNumber ifTrue: [ self collect: [: each | each * number ] ] ifFalse: [ self mulMatrix: numberOrMatrix ] as you can see, a #collect: method can be used for scalar multiplication.
Cheers
r. _______________________________________________ Pharo-project mailing list Pharo-project@lists.gforge.inria.fr http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
-- Best regards, Igor Stasenko AKA sig. _______________________________________________ Pharo-project mailing list Pharo-project@lists.gforge.inria.fr http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project This email is confidential and subject to important disclaimers and conditions including on offers for the purchase or sale of securities, accuracy and completeness of information, viruses, confidentiality, legal privilege, and legal entity disclaimers, available at http://www.jpmorgan.com/pages/disclosures/email.