For C programmers, another way to look at blocks is that it is like passing a function pointer, except that instead of specifying the address of a function that you wrote elsewhere, you just write the text of the function.
On 10/14/08, Ron Teitelbaum <[EMAIL PROTECTED]> wrote: > > Hi Tony, > > You stumbled on one of the most powerful features of Smalltalk. The Block > (See BlockContext). Blocks are a contextual memory space. They can be > passed around and do all sorts of great things that Smalltalk programmers > take for granted. > > The basic form is [] this is a no argument, no code block. Pretty boring > cause it does nothing. > > A more advanced form is ['hello'] which is a block with a literal string. > Still pretty boring. But at least you can get the string out of the block > by aBlock := ['hello']. ^aBlock value. > > A bit more advanced: [:arg | 'Hello ', arg] has an argument. > Now you can do ^aBlock value: 'Ron'. > > You can have more arguments [:arg1 :arg2 | 'Hello ', arg1, ' ', arg2]. > > Now you can do ^aBlock value: self firstName value: self lastName. > > Even more complicated is: > | isLoggedIn | > > isLoggedIn := true. > > [:arg | 'Hello ', arg, ' you are ', (isLoggedIn ifTrue: [''] ifFalse: [' > not']), ' logged in'] > > Now you can do ^aBlock value: 'Ron'. From anywhere and the block remembers > the context from where it was created. Pretty cool huh. > > The regular select uses a block too: > > self select: [:anItem | anItem isBlue] > > which uses a do that uses a block > > self do: [:anElement | > aBlock value: anElement) ifTrue ... > ] > > Blocks are certainly a good thing to learn. > > Happy Coding, > Ron Teitelbaum > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:beginners- > > [EMAIL PROTECTED] On Behalf Of Tony Giaccone > > Sent: Tuesday, October 14, 2008 2:12 AM > > To: beginners@lists.squeakfoundation.org > > Subject: [Newbies] Total newb... > > > > Ok, so I'm really new to smalltalk. I've done a few basic tutorials > > and have a simple understanding of the syntax. My pervious programing > > experience is mostly java/C with a bit of Objective C in the mix. > > > > I'm trying to figure out how to do what seems like a simple thing. > > > > I have a set, I'd like to find out if an object exists in the set. > > > > In a general form. Let's use the a relatively simple case. > > > > Assume I have classes Rock Paper and Scissors. > > > > > > validHands := Set new. > > validHands add: Rock new; add Paper new; add Scissors new. > > > > Assume I have a player object which responds to the method > > throwsAHand with an instance of Rock Paper or Scissors. > > > > how do I craft > > > > validHands contains: aPlayer throwsAHand > > > > I know that contains: takes a block, and that this isn't correctly > > done.. but I'm trying to get the a handle on how to do this. > > The intent is to return a boolean, that indicates if the object the > > player threw is in the Set of valid objects that can be thrown. > > > > > > Tony > > > > > > _______________________________________________ > > Beginners mailing list > > Beginners@lists.squeakfoundation.org > > http://lists.squeakfoundation.org/mailman/listinfo/beginners > > _______________________________________________ > Beginners mailing list > Beginners@lists.squeakfoundation.org > http://lists.squeakfoundation.org/mailman/listinfo/beginners >
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