Re: [Pharo-users] A "with" construct like Pascal - easy to do, but is it terrible?
The Pascal 'with' statement is among the most hated features of Pascal and was not copied in successor languages like Ada or Modula-2. It was typically replaced by record constructors, such as Book1 := Book[title : 'C Programming'; author : 'Nuha Ali '; subject : 'C Programming Tutorial'; book_id : 6495407]; which happens to be Pascal (ISO10206). In self classes do: [:class | | metaclass | metaclass := class metaclass. metaclass . mataclass . ] "metaclass" is a a block temporary, not an instance variable, and self classes do: [:each | (each metaclass) ; ]. suffices. We observe that [:x1 ... :xn | ...] value: e1 ... value: en is nothing other than a LET expression wearing a funny hat and should be inlined by a compiler -- mine does -- and that e1 in: [:x1 | ...] is just a "flipped" version of [:x1 | ...] value: e1, so there's no reason why a compiler shouldn't inline that. We also observe that e0 m1; ... ; mn can -- at least in my experience -- be most simply implemented as [:t | t m1. ... t mn] value: e0 followed by the usual inlining of that. So we might expect that some day self classes do: [:each | each metaclass in: [:t | t . t ]] would generate the *same* code as the cascaded version. Right now, do whichever is clearer. On Tue, 5 Mar 2019 at 02:07, Tim Mackinnon wrote: > I’ve noticed that as we’ve progressed there has been a move to more > concise and fluid code - e.g. I quite like the new String streaming stuff > > e.g. > > ^ String > streamContents: [ :stream | > stream nextPut: …. ] > > > So I was wondering why we don’t have a construct like Pascals with to > avoid Book1.title, Book1.author etc. > > (* book 1 specification *)With Book1 dobegin >title := 'C Programming'; >author := 'Nuha Ali '; >subject := 'C Programming Tutorial'; >book_id := 6495407;end; > > > I often find it a bit tedious with code like the following which then > needs an instvar... > > self classes do: [ :class | > | metaclass | > metaclass := class metaclass. > metaclass . > mataclass . > ] > > > I’m wondering why we don’t have #with:do: > > class with: class metaclass do: [:metaclass | > metaclass xxx. > ] > > > But when such things aren’t there - there is usually a good reason and I’m > curious … this said, there are all kinds of other such tricks (which I > rarely use that I keep coming across). > > Tim > >
Re: [Pharo-users] A "with" construct like Pascal - easy to do, but is it terrible?
On 4. 3. 2019 14:15, Esteban Maringolo wrote: Well... you have the cascading that provides you that. book1 title:'C Programming'; author: 'Nuha Ali '; subject: 'C Programming Tutorial'; book_id: 6495407. What I would like, sometimes, is the option to nest cascades, very much like the WITH DO construct of Pascal, Basic and others. Shameless plug: https://blog.herby.sk/post/customizing-cascade. Some year(s) ago I did a poll in twitter in ppl would like this in Amber. It was 5 for, 5 against. Herby But also I take this as a hint of some refactoring needed in my objects. Regards, Esteban A. Maringolo
Re: [Pharo-users] A "with" construct like Pascal - easy to do, but is it terrible?
> On 4 Mar 2019, at 13:59, Christian Haider > wrote: > > Or #ifNotNil: When you are in the right mindset - lots of things come out of the wood work...
Re: [Pharo-users] A "with" construct like Pascal - easy to do, but is it terrible?
> On 4 Mar 2019, at 13:34, Sven Van Caekenberghe wrote: > > There is #in: that does exactly that: Classic - it was there - you just needed to get the name right. thanks.
Re: [Pharo-users] A "with" construct like Pascal - easy to do, but is it terrible?
Or #ifNotNil: class metaclass ifNotNil: [ :metaclass | metaclass xxx. metaclass yyy ]. With the added benefit to not do anything with nil. Christian > -Ursprüngliche Nachricht- > Von: Pharo-users Im Auftrag von > Sven Van Caekenberghe > Gesendet: Montag, 4. März 2019 14:35 > An: Any question about pharo is welcome > Betreff: Re: [Pharo-users] A "with" construct like Pascal - easy to do, but > is it > terrible? > > There is #in: that does exactly that: > > class metaclass in: [ :metaclass | > metaclass xxx. > metaclass yyy ]. > > This is quite similar to lisp's let. > > You can do almost anything with blocks/closures. > > Although not relevant in most cases, there is a small performance price to > pay - but again this is only relevant inside performance critical loops. > > > On 4 Mar 2019, at 14:06, Tim Mackinnon wrote: > > > > I’ve noticed that as we’ve progressed there has been a move to more > concise and fluid code - e.g. I quite like the new String streaming stuff > > > > e.g. > > > > ^ String > > streamContents: [ :stream | > > stream nextPut: …. ] > > > > > > So I was wondering why we don’t have a construct like Pascals with to > avoid Book1.title, Book1.author etc. > > > > (* book 1 specification *) > > With Book1 do > > begin > > > >title > > := 'C Programming'; > > > >author > > := 'Nuha Ali '; > > > >subject > > := 'C Programming Tutorial'; > > > >book_id > > := 6495407; > > end; > > > > I often find it a bit tedious with code like the following which then needs > > an > instvar... > > > > self classes do: [ :class | > > | metaclass | > > metaclass := class metaclass. > > metaclass . > > mataclass . > > ] > > > > > > I’m wondering why we don’t have #with:do: > > > > class with: class metaclass do: [:metaclass | > > metaclass xxx. > > ] > > > > > > But when such things aren’t there - there is usually a good reason and I’m > curious … this said, there are all kinds of other such tricks (which I rarely > use > that I keep coming across). > > > > Tim > > >
Re: [Pharo-users] A "with" construct like Pascal - easy to do, but is it terrible?
There is #in: that does exactly that: class metaclass in: [ :metaclass | metaclass xxx. metaclass yyy ]. This is quite similar to lisp's let. You can do almost anything with blocks/closures. Although not relevant in most cases, there is a small performance price to pay - but again this is only relevant inside performance critical loops. > On 4 Mar 2019, at 14:06, Tim Mackinnon wrote: > > I’ve noticed that as we’ve progressed there has been a move to more concise > and fluid code - e.g. I quite like the new String streaming stuff > > e.g. > > ^ String > streamContents: [ :stream | > stream nextPut: …. ] > > > So I was wondering why we don’t have a construct like Pascals with to avoid > Book1.title, Book1.author etc. > > (* book 1 specification *) > With Book1 do > begin > >title > := 'C Programming'; > >author > := 'Nuha Ali '; > >subject > := 'C Programming Tutorial'; > >book_id > := 6495407; > end; > > I often find it a bit tedious with code like the following which then needs > an instvar... > > self classes do: [ :class | > | metaclass | > metaclass := class metaclass. > metaclass . > mataclass . > ] > > > I’m wondering why we don’t have #with:do: > > class with: class metaclass do: [:metaclass | > metaclass xxx. > ] > > > But when such things aren’t there - there is usually a good reason and I’m > curious … this said, there are all kinds of other such tricks (which I rarely > use that I keep coming across). > > Tim >
Re: [Pharo-users] A "with" construct like Pascal - easy to do, but is it terrible?
Well... you have the cascading that provides you that. book1 title:'C Programming'; author: 'Nuha Ali '; subject: 'C Programming Tutorial'; book_id: 6495407. What I would like, sometimes, is the option to nest cascades, very much like the WITH DO construct of Pascal, Basic and others. But also I take this as a hint of some refactoring needed in my objects. Regards, Esteban A. Maringolo El lun., 4 mar. 2019 a las 10:07, Tim Mackinnon () escribió: > > I’ve noticed that as we’ve progressed there has been a move to more concise > and fluid code - e.g. I quite like the new String streaming stuff > > e.g. > > ^ String > streamContents: [ :stream | > stream nextPut: …. ] > > > So I was wondering why we don’t have a construct like Pascals with to avoid > Book1.title, Book1.author etc. > > (* book 1 specification *) > With Book1 do > begin >title := 'C Programming'; >author := 'Nuha Ali '; >subject := 'C Programming Tutorial'; >book_id := 6495407; > end; > > > I often find it a bit tedious with code like the following which then needs > an instvar... > > self classes do: [ :class | > | metaclass | > metaclass := class metaclass. > metaclass . > mataclass . > ] > > > I’m wondering why we don’t have #with:do: > > class with: class metaclass do: [:metaclass | > metaclass xxx. > ] > > > But when such things aren’t there - there is usually a good reason and I’m > curious … this said, there are all kinds of other such tricks (which I rarely > use that I keep coming across). > > Tim >
[Pharo-users] A "with" construct like Pascal - easy to do, but is it terrible?
I’ve noticed that as we’ve progressed there has been a move to more concise and fluid code - e.g. I quite like the new String streaming stuff e.g. ^ String streamContents: [ :stream | stream nextPut: …. ] So I was wondering why we don’t have a construct like Pascals with to avoid Book1.title, Book1.author etc. (* book 1 specification *) With Book1 do begin title := 'C Programming'; author := 'Nuha Ali '; subject := 'C Programming Tutorial'; book_id := 6495407; end; I often find it a bit tedious with code like the following which then needs an instvar... self classes do: [ :class | | metaclass | metaclass := class metaclass. metaclass . mataclass . ] I’m wondering why we don’t have #with:do: class with: class metaclass do: [:metaclass | metaclass xxx. ] But when such things aren’t there - there is usually a good reason and I’m curious … this said, there are all kinds of other such tricks (which I rarely use that I keep coming across). Tim
