Thanks Ben – it’s all clear now. Thanks also to Esteban, who spared my blushes by answering direct! Peter Kenny From: Pharo-users <pharo-users-bounces@lists.pharo.org> On Behalf Of Ben Coman Sent: 10 September 2018 19:56 To: Any question about pharo is welcome <pharo-users@lists.pharo.org> Subject: Re: [Pharo-users] Query on Pharo syntax On Tue, 11 Sep 2018 at 02:44, PBKResearch <peter@pbkresearch.co.uk <mailto:peter@pbkresearch.co.uk> > wrote: Hi All This is an idiot question, I should know the answer, but I have looked around and can’t find relevant documentation. I’m not asking for a full answer, just a pointer as to where to start looking. I have seen from examples in this forum that an expression like the following: paras collect: [para| para prettyPrinted] can be written more concisely as: paras collect: #prettyPrinted which obviously works when I try it. It doesn’t seem to fit in with the definition of #collect:, which requires a block as argument. Where can I find the relevant definition, either in method comments or in some general manual? Can the notation be extended, Its not special notation. Just a normal object (a Symbol) passed via a normal message. for example to #select: - obviously with an argument which returns a Boolean? Can it be used with a method which requires an argument, e.g. as myArray collect: (#myMethod: arg)? Are there any other extensions? Any help gratefully received. Peter Kenny Full answer ;) Its a combination of the following two methods... Collection >> collect: aBlock | newCollection | newCollection := self species new. self do: [:each | newCollection add: (aBlock value: each)]. ^ newCollection Symbol value: anObject ^anObject perform: self. When /aBlock/ is a symbol, that symbol is performed on /each/ element. And looking at #select: , yes it works the same... Collection >> select: aBlock | newCollection | newCollection := self copyEmpty. self do: [ :each | (aBlock value: each) ifTrue: [ newCollection add: each ]]. ^newCollection cheers -ben

I learned something for sure from this exchange. Thanks Peter and Ben for this public conversation. Cheers, Offray On 9/10/18 7:56 PM, Ben Coman wrote:

Its a very interesting and elegant aspect of Pharo  and I'm sure there are others at different parts of their journey learning Pharo who learnt something new from your question. 

cheers -ben

On Tue, 11 Sep 2018 at 03:13, PBKResearch <peter@pbkresearch.co.uk <mailto:peter@pbkresearch.co.uk>> wrote:

Thanks Ben – it’s all clear now. Thanks also to Esteban, who spared my blushes by answering direct!

Peter Kenny

 

*From:*Pharo-users <pharo-users-bounces@lists.pharo.org <mailto:pharo-users-bounces@lists.pharo.org>> *On Behalf Of *Ben Coman *Sent:* 10 September 2018 19:56 *To:* Any question about pharo is welcome <pharo-users@lists.pharo.org <mailto:pharo-users@lists.pharo.org>> *Subject:* Re: [Pharo-users] Query on Pharo syntax

 

 

On Tue, 11 Sep 2018 at 02:44, PBKResearch <peter@pbkresearch.co.uk <mailto:peter@pbkresearch.co.uk>> wrote:

Hi All

 

This is an idiot question, I should know the answer, but I have looked around and can’t find relevant documentation. I’m not asking for a full answer, just a pointer as to where to start looking.

 

I have seen from examples in this forum that an expression like the following:

 

paras collect: [para| para prettyPrinted]

 

can be written more concisely as:

 

paras collect: #prettyPrinted

 

which obviously works when I try it. It doesn’t seem to fit in with the definition of #collect:, which requires a block as argument. Where can I find the relevant definition, either in method comments or in some general manual? Can the notation be extended,

 

Its not special notation.  Just a normal object (a Symbol) passed via a normal message.

 

for example to #select: - obviously with an argument which returns a Boolean? Can it be used with a method which requires an argument, e.g. as myArray collect: (#myMethod: arg)? Are there any other extensions?

 

Any help gratefully received.

 

Peter Kenny

 

Full answer ;)

Its a combination of the following two methods...

 

Collection >> collect: aBlock 

               | newCollection |

               newCollection := self species new.

               self do: [:each | newCollection add: (aBlock value: each)].

               ^ newCollection 

 

Symbol value: anObject 

               ^anObject perform: self.

 

When /aBlock/ is a symbol, that symbol is performed on /each/ element.

And looking at  #select:  , yes it works the same... 

 

Collection >> select: aBlock 

               | newCollection |

               newCollection := self copyEmpty.

               self do: [ :each | 

                              (aBlock value: each) 

                                             ifTrue: [ newCollection add: each ]].

               ^newCollection

 

cheers -ben