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> 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