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Use of -> in Pharo Code

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bprior

Nov 30, 2016; 2:36am

Use of -> in Pharo Code

61 posts

I have been away from smalltalk coding for a while. On returning to the fold, I often see the use of a right arrow in code. Is this something new?

Today in a Teapot app example, I saw,

Teapot on GET: '/welcome' -> 'Hello World!'; start.

What is the arrow for?

Pharo Smalltalk Users mailing list

Nov 30, 2016; 2:45am

Re: Use of -> in Pharo Code

914 posts

Hi Bruce,

good to see you around, again!

The arrow is an Association in short...

Sebastian

Am 29.11.2016 um 18:48 schrieb Bruce Prior:

I have been away from smalltalk coding for a while. On returning to the fold, I often see the use of a right arrow in code. Is this something new?

Today in a Teapot app example, I saw,

Teapot on GET: '/welcome' -> 'Hello World!'; start.

What is the arrow for?

Martin McClure-2

Nov 30, 2016; 5:13am

Re: Use of -> in Pharo Code

285 posts

In reply to this post by bprior

On 11/29/2016 06:48 PM, Bruce Prior wrote:

I have been away from smalltalk coding for a while. On returning to the fold, I often see the use of a right arrow in code. Is this something new?

Today in a Teapot app example, I saw,

Teapot on GET: '/welcome' -> 'Hello World!'; start.

What is the arrow for?

As Sebastian said, #-> is a message that creates an Association, with the receiver as the key and the argument as the value of the Association. This has actually been around a very long time, though perhaps it's getting more widely used these days. It doesn't appear to be in the Blue Book, but I think it was probably actually in the Smalltalk-80 image 1 release.

I'm not *quite* curious enough to verify that by rooting around in my basement for the machine that actually runs that version and seeing if it will still power up after all these years. :-)

Regards,

-Martin

philippeback

Nov 30, 2016; 6:03am

Re: Use of -> in Pharo Code

3147 posts

Would be nice to have a video with that.

Phil

On Wed, Nov 30, 2016 at 6:25 AM, Martin McClure <[hidden email]> wrote:

On 11/29/2016 06:48 PM, Bruce Prior wrote:

I have been away from smalltalk coding for a while. On returning to the fold, I often see the use of a right arrow in code. Is this something new?

Today in a Teapot app example, I saw,

Teapot on GET: '/welcome' -> 'Hello World!'; start.

What is the arrow for?

As Sebastian said, #-> is a message that creates an Association, with the receiver as the key and the argument as the value of the Association. This has actually been around a very long time, though perhaps it's getting more widely used these days. It doesn't appear to be in the Blue Book, but I think it was probably actually in the Smalltalk-80 image 1 release.

I'm not *quite* curious enough to verify that by rooting around in my basement for the machine that actually runs that version and seeing if it will still power up after all these years. :-)

Regards,

-Martin

... [show rest of quote]

David T. Lewis

Nov 30, 2016; 12:41pm

Re: Use of -> in Pharo Code

7165 posts

In reply to this post by Martin McClure-2

On Tue, Nov 29, 2016 at 09:25:18PM -0800, Martin McClure wrote:

> On 11/29/2016 06:48 PM, Bruce Prior wrote:
> >I have been away from smalltalk coding for a while. On returning to
> >the fold, I often see the use of a right arrow in code. Is this
> >something new?
> >
> >Today in a Teapot app example, I saw,
> >
> >Teapot on GET: '/welcome' -> 'Hello World!'; start.
> >
> >What is the arrow for?
>
> As Sebastian said, #-> is a message that creates an Association, with
> the receiver as the key and the argument as the value of the
> Association. This has actually been around a very long time, though
> perhaps it's getting more widely used these days. It doesn't appear to
> be in the Blue Book, but I think it was probably actually in the
> Smalltalk-80 image 1 release.
>
> I'm not *quite* curious enough to verify that by rooting around in my
> basement for the machine that actually runs that version and seeing if
> it will still power up after all these years. :-)
>
> Regards,
>
> -Martin
>

... [show rest of quote]

It is present in the Squeak 1.13 image of 1996, which I think is fairly
close to Blue Book.

You can run that original image from this web page:

http://try.squeak.org

Dave

stepharo

Nov 30, 2016; 8:09pm

Re: Use of -> in Pharo Code

5159 posts

In reply to this post by bprior

Hi bruce

welcome and I hope that you have fun.

What I noticed is that we get used really fast to supercool tools. Last year I had to work on a VW 2.5 version

and I thought someone had cut my hands. I ws so slow with senders and implementors and rudimentary inspectors :)

Stef

I have been away from smalltalk coding for a while. On returning to the fold, I often see the use of a right arrow in code. Is this something new?

Today in a Teapot app example, I saw,

Teapot on GET: '/welcome' -> 'Hello World!'; start.

What is the arrow for?

Using Opera's mail client: http://www.opera.com/mail/

bprior

Dec 01, 2016; 12:00am

Re: Use of -> in Pharo Code

61 posts

In reply to this post by bprior

Hi Stef,

Thanks for the welcome back. I always have fun with Smalltalk in the Winter but each year Summer seems to get in the way.

I appreciate your reminiscences, but I still don't understand what the right aero (->) does.

Bruce

On 2016-11-30 12:21 PM, stepharo wrote:

Hi bruce

welcome and I hope that you have fun.

What I noticed is that we get used really fast to supercool tools. Last year I had to work on a VW 2.5 version

and I thought someone had cut my hands. I ws so slow with senders and implementors and rudimentary inspectors :)

Stef

I have been away from smalltalk coding for a while. On returning to the fold, I often see the use of a right arrow in code. Is this something new?

Today in a Teapot app example, I saw,

Teapot on GET: '/welcome' -> 'Hello World!'; start.

What is the arrow for?

--

Using Opera's mail client: http://www.opera.com/mail/

... [show rest of quote]

Pharo Smalltalk Users mailing list

Dec 01, 2016; 12:09am

Re: Use of -> in Pharo Code

914 posts

Hi Bruce,

in hsort again ;-)
This was your code:

Teapot on GET: '/welcome' -> 'Hello World!'; start.

Imagine it this way with brackets:

Teapot on GET: ('/welcome' -> 'Hello World!'); start.

This is the same as writing:

Teapot on GET: ( Associtation key: '/welcome' value: 'Hello World!') ; start.

Shorter:

(x -> y) = (Association key: x value: y)

The -> is the short version of the Association constructor.

I hope this makes things a little clearer.
Sebastian

Ben Coman

Dec 01, 2016; 12:50am

Re: Use of -> in Pharo Code

5447 posts

In reply to this post by bprior

On Thu, Dec 1, 2016 at 8:12 AM, Bruce Prior <[hidden email]> wrote:
> don't understand what the right-arrow (->) does.

hi Bruce,

Its a message. Select it and hit <ctrl-m> to view its implementation.

cheers -ben