Re: [Esug-list] metaprogramming in smalltalk
Nice! Almost as elegant as Ward's legendary Symbol>>value: anObject ^anObject perform: self
Mickey!) I don't understand how does it help me. The method is called #perform:with: and it takes two arguments. Yes. But what if I need to emulate "x perform: y with: z" - there is three arguments How can I do this using perform? Yes, there is Behavior class that compile everything so non can help this method is good. But what about perform? Message class also require selector and what is selector for keyword messages? 2012/4/29 Jean-François LEFEVRE <jflefevre@gmail.com>
You probably want to do something like this :
| x y plu perf wi args | x := 3. y := 4. plu := '+'. perf := 'perform:withArguments:'. args := Array new: 1. args at: 1 put: y. x perform: perf asSymbol withArguments: args
You should look the class Message too. (and all other classes and methods like Behavior, Class, Metaclass, Method and Object)
Jean-François
2012/4/29 Vitaly Kosenko <vitaly.kosenko@gmail.com>
Ok. perform: is working for arithmetic but what about perform: itself? | x y plu perf wi args | x := 3. y := 4. plu := '+'. perf := 'perform:'. wi := 'with:'. args := Array new: 3. args at: 1 put: plu asSymbol; at: 2 put: wi asSymbol; at: 3 put: y. x perform: perf asSymbol withArguments: args.
This code tells me that there is wrong number of arguments in permforn: How can I fix it?
2012/4/29 vittly <vitaly.kosenko@gmail.com>
Mmm thnx for replie! I'll run this code and experemt with it
2012/4/29 Georg Heeg [via Smalltalk] <[hidden email]<http://user/SendEmail.jtp?type=node&node=4596244&i=0>
Please try to understand the following code:
| a b c |
a := 3. b := 4. c := '+'. ^a perform: c asSymbol with: b
Georg Heeg eK, Dortmund und Köthen, HR Dortmund A 12812 Wallstraße 22, 06366 Köthen Tel. +49-3496-214328, Fax +49-3496-214712
-----Ursprüngliche Nachricht----- Von: [hidden email]<http://user/SendEmail.jtp?type=node&node=4596217&i=0> [mailto:[hidden email]<http://user/SendEmail.jtp?type=node&node=4596217&i=1>] Im Auftrag von vittly Gesendet: Sonntag, 29. April 2012 10:25 An: [hidden email]<http://user/SendEmail.jtp?type=node&node=4596217&i=2> Betreff: [Esug-list] metaprogramming in smalltalk
Hi! Please could you help me understand smalltalk capabilities in metaprogramming? Q: could I construct arbitrary message by program? Create keywords from strings and than build sequence of them to make a message. Mm? Or may be store keywords in variables and then pass variables withing messages extracting stored keywords? Am I dreamer?)
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Hi Vitaly! try to think it like this: #perform:with: is a reflective operation to send messags to an object. Thus, if you are trying to send an object a message like: object perform: someSelector with: someArgument. - The receiver is object - the selector of the message is #perform:with: - the arguments of #perform:with: are someSelector and someArgument. Then, what you have to do is object perform: #perform:with: withArguments: { someSelector . someArgument } Because #perform: and #with: are not two different messages, they are two keywords of the same selector, in the same message. Then, you have to treat them together. Cheers, Guille 2012/4/29 Vitaly Kosenko <vitaly.kosenko@gmail.com>
Nice! Almost as elegant as Ward's legendary
Symbol>>value: anObject ^anObject perform: self
Mickey!) I don't understand how does it help me.
The method is called #perform:with: and it takes two arguments.
Yes. But what if I need to emulate "x perform: y with: z" - there is three arguments
How can I do this using perform?
Yes, there is Behavior class that compile everything so non can help this method is good. But what about perform? Message class also require selector and what is selector for keyword messages?
2012/4/29 Jean-François LEFEVRE <jflefevre@gmail.com>
You probably want to do something like this :
| x y plu perf wi args | x := 3. y := 4. plu := '+'. perf := 'perform:withArguments:'. args := Array new: 1. args at: 1 put: y. x perform: perf asSymbol withArguments: args
You should look the class Message too. (and all other classes and methods like Behavior, Class, Metaclass, Method and Object)
Jean-François
2012/4/29 Vitaly Kosenko <vitaly.kosenko@gmail.com>
Ok. perform: is working for arithmetic but what about perform: itself? | x y plu perf wi args | x := 3. y := 4. plu := '+'. perf := 'perform:'. wi := 'with:'. args := Array new: 3. args at: 1 put: plu asSymbol; at: 2 put: wi asSymbol; at: 3 put: y. x perform: perf asSymbol withArguments: args.
This code tells me that there is wrong number of arguments in permforn: How can I fix it?
2012/4/29 vittly <vitaly.kosenko@gmail.com>
Mmm thnx for replie! I'll run this code and experemt with it
2012/4/29 Georg Heeg [via Smalltalk] <[hidden email]<http://user/SendEmail.jtp?type=node&node=4596244&i=0>
Please try to understand the following code:
| a b c |
a := 3. b := 4. c := '+'. ^a perform: c asSymbol with: b
Georg Heeg eK, Dortmund und Köthen, HR Dortmund A 12812 Wallstraße 22, 06366 Köthen Tel. +49-3496-214328, Fax +49-3496-214712
-----Ursprüngliche Nachricht----- Von: [hidden email]<http://user/SendEmail.jtp?type=node&node=4596217&i=0> [mailto:[hidden email]<http://user/SendEmail.jtp?type=node&node=4596217&i=1>] Im Auftrag von vittly Gesendet: Sonntag, 29. April 2012 10:25 An: [hidden email]<http://user/SendEmail.jtp?type=node&node=4596217&i=2> Betreff: [Esug-list] metaprogramming in smalltalk
Hi! Please could you help me understand smalltalk capabilities in metaprogramming? Q: could I construct arbitrary message by program? Create keywords from strings and than build sequence of them to make a message. Mm? Or may be store keywords in variables and then pass variables withing messages extracting stored keywords? Am I dreamer?)
-- View this message in context:
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| x y plu perf wi sel args | x := 3. y := 4. plu := '+'. perf := 'perform:'. wi := 'with:'. sel := perf,wi. args := Array new: 2. args at: 1 put: plu asSymbol; at: 2 put: y. x perform: sel asSymbol withArguments: args. It works! Great! Thanks a lot. About Pharo examples book: I have red some chapters but the real understanding comes only in prectice) 2012/4/30 Guillermo Polito <guillermopolito@gmail.com>
Hi Vitaly!
try to think it like this: #perform:with: is a reflective operation to send messags to an object. Thus, if you are trying to send an object a message like:
object perform: someSelector with: someArgument.
- The receiver is object - the selector of the message is #perform:with: - the arguments of #perform:with: are someSelector and someArgument.
Then, what you have to do is
object perform: #perform:with: withArguments: { someSelector . someArgument }
Because #perform: and #with: are not two different messages, they are two keywords of the same selector, in the same message. Then, you have to treat them together.
Cheers, Guille
2012/4/29 Vitaly Kosenko <vitaly.kosenko@gmail.com>
Nice! Almost as elegant as Ward's legendary
Symbol>>value: anObject ^anObject perform: self
Mickey!) I don't understand how does it help me.
The method is called #perform:with: and it takes two arguments.
Yes. But what if I need to emulate "x perform: y with: z" - there is three arguments
How can I do this using perform?
Yes, there is Behavior class that compile everything so non can help this method is good. But what about perform? Message class also require selector and what is selector for keyword messages?
2012/4/29 Jean-François LEFEVRE <jflefevre@gmail.com>
You probably want to do something like this :
| x y plu perf wi args | x := 3. y := 4. plu := '+'. perf := 'perform:withArguments:'. args := Array new: 1. args at: 1 put: y. x perform: perf asSymbol withArguments: args
You should look the class Message too. (and all other classes and methods like Behavior, Class, Metaclass, Method and Object)
Jean-François
2012/4/29 Vitaly Kosenko <vitaly.kosenko@gmail.com>
Ok. perform: is working for arithmetic but what about perform: itself? | x y plu perf wi args | x := 3. y := 4. plu := '+'. perf := 'perform:'. wi := 'with:'. args := Array new: 3. args at: 1 put: plu asSymbol; at: 2 put: wi asSymbol; at: 3 put: y. x perform: perf asSymbol withArguments: args.
This code tells me that there is wrong number of arguments in permforn: How can I fix it?
2012/4/29 vittly <vitaly.kosenko@gmail.com>
Mmm thnx for replie! I'll run this code and experemt with it
2012/4/29 Georg Heeg [via Smalltalk] <[hidden email]<http://user/SendEmail.jtp?type=node&node=4596244&i=0>
Please try to understand the following code:
| a b c |
a := 3. b := 4. c := '+'. ^a perform: c asSymbol with: b
Georg Heeg eK, Dortmund und Köthen, HR Dortmund A 12812 Wallstraße 22, 06366 Köthen Tel. +49-3496-214328, Fax +49-3496-214712
-----Ursprüngliche Nachricht----- Von: [hidden email]<http://user/SendEmail.jtp?type=node&node=4596217&i=0> [mailto:[hidden email]<http://user/SendEmail.jtp?type=node&node=4596217&i=1>] Im Auftrag von vittly Gesendet: Sonntag, 29. April 2012 10:25 An: [hidden email]<http://user/SendEmail.jtp?type=node&node=4596217&i=2> Betreff: [Esug-list] metaprogramming in smalltalk
Hi! Please could you help me understand smalltalk capabilities in metaprogramming? Q: could I construct arbitrary message by program? Create keywords from strings and than build sequence of them to make a message. Mm? Or may be store keywords in variables and then pass variables withing messages extracting stored keywords? Am I dreamer?)
-- View this message in context:
http://forum.world.st/metaprogramming-in-smalltalk-tp4595928p4595928.html Sent from the ESUG mailing list archive at Nabble.com.
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participants (2)
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Guillermo Polito -
Vitaly Kosenko