[Newbies] Re: Smalltalk is a Mystery to Me

Fri Aug 22 17:33:55 UTC 2008

Squeak by Example is a great FREE book you can download.  I use it as a kind
of reference sometimes when programming, I think you should check it out.
http://squeakbyexample.org

On Fri, Aug 22, 2008 at 12:18 PM, nicolas cellier <ncellier at ifrance.com>wrote:

> Tcykgreis at aol.com a écrit :
>
>> I have had a curiosity about Smalltalk for many years so I recently
>> downloaded and installed Squeak. That's when the trouble began. I have
>> written applications that deal bridge hands and either display the hands on
>> screen or save them in a couple of different formats. I originally wrote the
>> 'words' in Forth. I later tried Ruby and rewrote most of the programs in
>> Ruby. I did it as a learning experience. I sat out to do the same thing in
>> Squeak, again as a learning experience, but have made virtually no progress.
>> I create the class 'Bridge' with the subclass of dealer. I try to initialize
>> by filling a byteArray with 52 numbers, 0 through 51. I tended to create
>> additional methods to shuffle and deal the cards to four more byte arrays
>> named north, east, south, and west. Eventually I will need another method to
>> "stack the deck." I will also need a counter to keep track of the deal
>> number.
>>  I can't get started, and I mean zero progress, because I can't create and
>> load deck. It seems like the documentation is never quit up to date. I read
>> about curly braces and tried deck := {0. 1. 2. ... }. When I try to accept
>> it, first deck is questioned and then after deck I get something about not
>> expecting anything else.
>>
>
> What kind of Object is a Bridge? to me it sounds more like a namespace than
> an Object.
> What kind of object is a Dealer? Maybe you mean a Deal?
> What are the instance variable of your class?
> What are its main methods (the messages than Dealer will respond to) you
> want to implement?
>
> You really have to think in term of Objects and messages, otherwise your
> Smalltalk experience won't be that nice.
>
> Maybe you want to create an initialize method in Dealer, assuming deck is
> an instance variable:
>
> initialize
>        deck := (1 to: 52) asOrderedCollection shuffled.
>
> Then, when you create a Dealer object (Dealer new), its instance variable
> will be initialized.
>
>  I know there is a word 'asByteArray:' and I assume a number would specify
>> the size of the array but nowhere can I find anything about the order in
>> which the information should be provided. I tried deck asByteArray: 52 but I
>> don't know if it worked. If it did work, how do I load the bytes into it?
>> How do I look at a byte in a particular location in the array? Can I remove
>> a byte from position x and/or insert a byte at position y and everything
>> moves to accommodate the change.
>>
>>
>
> | ba |
> ba := ByteArray new: 52. "Create a ByteArray with 52 bytes"
> ba at: 5 put: 23. "set the fith element to 23"
>
> (1 to: 52) asByteArray. "Try to evaluate this..."
>
> (1 to: 52) asByteArray shuffled. "That might be of interest"
>
> If you want to insert and remove, I recommend you begin with an
> OrderedCollection. OrderedCollection are growable and support adding and
> removing elements easily (you'll have to browse existing messages or get
> help from Squeak by example book which is excellent for beginners).
>
> An Array has a fixed size and must be copied if you want to insert/remove
> elements.
> You can inquire about #copyReplaceFrom:to:with:
>
> ba := ba copyReplaceFrom: 3 to: 4 with: ByteArray new. "remove third and
> fourth elements"
>
> ba := ba copyReplaceFrom: 3 to: 2 with: {11. 22.} asByteArray. "insert 11
> and 22 at third and fourth position"
>
>  In Forth and Ruby, I was able to store the hands as a 2D bit array, 4
>> suits and 13 bits. If the card was present the bit was set. When I dealt the
>> cards, the appropriate bits were set.. This worked really well. The suits
>> came out already sorted. The strength of a suit turned out to be related to
>> the value stored for the suit. The number of cards in the suit could be
>> found by counting set bits. I have yet to find bit-manipulating words in
>> Squeak/Smalltalk.
>>  As an aside, the least number of bits that must be used to store a
>> complete deal is 104 or 13 bytes. The bits are arranged in 52 2-bit groups.
>> The position in the array represents the value of the card and the bits
>> determine which hands gets the card represented by that position. When you
>> shuffle the 2-bit groups must be kept in tact. I could easily do this in
>> Forth but could not do it in Ruby. If you are going to save a few million
>> hands, it is nice to be able to do so in this most compact form.
>>
>>
> I strongly recommend you write a non optimized version to begin with.
> Squeak has enough support for collection to shuffle sort add remove select
> reject etc...
>
> Then only when you get used to objects and messages, you should inquire
> about optimizing space with bits in bit arrays.
>
> Note that it's absolutely doable in Squeak, but you'll may have to write
> some of the base methods. I think Yoshiki Oshima have quite an advanced
> implementation of BitArray, take a look at SqueakMap (from World menu
> Open...).
>
>
>  If I could just figure out where to find the answers to these beginner
>> question, I would really appreciate it. It would also be nice if I could see
>> some examples of these methods.
>>  Charlie
>>
>>
>
> Maybe a look at free book Squeak by Example would be a good start to get
> acquainted to Smalltalk.
>
> Cheers
>
>
>>
>> ------------------------------------------------------------------------
>> It's only a deal if it's where /you/ want to go. Find your travel deal
>> *here* <http://information.travel.aol.com/deals?ncid=aoltrv00050000000047
>> >.
>>
>>
>> ------------------------------------------------------------------------
>>
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>
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-- 
David Zmick
/dz0004455\
http://dz0004455.googlepages.com
http://dz0004455.blogspot.com
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