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Pharo-users Question about the symbols

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Valentin Ryckewaert

Pharo-users Question about the symbols

Hello everyone,

i'm learning Pharo and i'm having difficulties to understand the symbols, what are they? How are they different of the ByteString ? Why are they usefull ?

Why should I put #string where I can put 'string' ?

Thanks in advance for your answer.

Valentin Ryckewaert

Ben Coman

Re: Pharo-users Question about the symbols

A symbol is like a string, except that all symbols with the same value
are in fact the same object; that is, every #hello symbol is the exact
same object as every other #hello symbol.

See "identically equal" section here...
http://sdmeta.gforge.inria.fr/FreeBooks/ByExample/08%20-%20Chapter%206%20-%20Special%20Symbol.pdf

cheers, ben

On Fri, Apr 8, 2016 at 7:20 AM, Valentin Ryckewaert
<[hidden email]> wrote:
> Hello everyone,
>
> i'm learning Pharo and i'm having difficulties to understand the symbols,
> what are they? How are they different of the ByteString ? Why are they
> usefull ?
> Why should I put #string where I can put 'string' ?
>
> Thanks in advance for your answer.
> Valentin Ryckewaert

Markus Stumptner

Re: Pharo-users Question about the symbols

As a result, internal names (e.g., method names) are usually symbols.
Strings are normally used for string manipulation, symbols for
unambiguous (but humanly readable!) internal reference (vulgo 'naming').

Markus

On 08/04/16 10:53, Ben Coman wrote:

> A symbol is like a string, except that all symbols with the same value
> are in fact the same object; that is, every #hello symbol is the exact
> same object as every other #hello symbol.
>
> See "identically equal" section here...
> http://sdmeta.gforge.inria.fr/FreeBooks/ByExample/08%20-%20Chapter%206%20-%20Special%20Symbol.pdf
>
> cheers, ben
>
> On Fri, Apr 8, 2016 at 7:20 AM, Valentin Ryckewaert
> <[hidden email]> wrote:
>> Hello everyone,
>>
>> i'm learning Pharo and i'm having difficulties to understand the symbols,
>> what are they? How are they different of the ByteString ? Why are they
>> usefull ?
>> Why should I put #string where I can put 'string' ?
>>
>> Thanks in advance for your answer.
>> Valentin Ryckewaert
>

Brad Selfridge

Re: Pharo-users Question about the symbols

And symbols are immutable

Brad

Sent from my iPad

> On Apr 7, 2016, at 9:41 PM, Markus Stumptner <[hidden email]> wrote:
>
> As a result, internal names (e.g., method names) are usually symbols. Strings are normally used for string manipulation, symbols for unambiguous (but humanly readable!) internal reference (vulgo 'naming').
>
> Markus
>
>
>> On 08/04/16 10:53, Ben Coman wrote:
>> A symbol is like a string, except that all symbols with the same value
>> are in fact the same object; that is, every #hello symbol is the exact
>> same object as every other #hello symbol.
>>
>> See "identically equal" section here...
>> http://sdmeta.gforge.inria.fr/FreeBooks/ByExample/08%20-%20Chapter%206%20-%20Special%20Symbol.pdf
>>
>> cheers, ben
>>
>> On Fri, Apr 8, 2016 at 7:20 AM, Valentin Ryckewaert
>> <[hidden email]> wrote:
>>> Hello everyone,
>>>
>>> i'm learning Pharo and i'm having difficulties to understand the symbols,
>>> what are they? How are they different of the ByteString ? Why are they
>>> usefull ?
>>> Why should I put #string where I can put 'string' ?
>>>
>>> Thanks in advance for your answer.
>>> Valentin Ryckewaert
>
>

Brad Selfridge

CyrilFerlicot

Re: Pharo-users Question about the symbols

In reply to this post by Valentin Ryckewaert

On Friday, 8 April 2016, Valentin Ryckewaert <[hidden email]> wrote:

Hello everyone,

i'm learning Pharo and i'm having difficulties to understand the symbols, what are they? How are they different of the ByteString ? Why are they usefull ?
Why should I put #string where I can put 'string' ?

Hi,

As the others said, symbols are some kind of string that are unique in the image. I would like to talk also about a super cool feature.

A Block can receive the message #value:. For example when you do a #do: on a collection, the block will receive multiple #value: message with the element in argument.

[ :class | class allSubclasses] value: Object.

And the cool feature is that Symbol also have this method, so with the polymorphism you can do:

#AllSubclasses value: Object

{ Object . Morph . Integer . Float } collect: #allSubclasses

This is a pretty cool feature that I wanted to share.

Thanks in advance for your answer.
Valentin Ryckewaert

Cheers

Cyril Ferlicot

Henrik Nergaard

Re: Pharo-users Question about the symbols

In reply to this post by Ben Coman

| s1 s2 |

s1 := 1234 asString.
s2 := 1234 asString.

s1 = s2. "true"
s1 == s2. "false"

s1 asSymbol = s2 asSymbol. "true"
s1 asSymbol == s2 asSymbol. "true"

(s1 class allInstances select: [:s | s = s1 ]) size. "2"
(s1 asSymbol class allInstances select: [:s | s = s1 asSymbol ]) size. "1"

[ #stringA = #stringB ] bench. "26,812,864 per second"
[ 'StringA' = 'StringB' ] bench. "3,492,987 per second"

Best regards,
Henrik

-----Original Message-----
From: Pharo-users [mailto:[hidden email]] On Behalf Of Ben Coman
Sent: Friday, April 8, 2016 3:23 AM
To: Any question about pharo is welcome <[hidden email]>
Subject: Re: [Pharo-users] Pharo-users Question about the symbols

A symbol is like a string, except that all symbols with the same value are in fact the same object; that is, every #hello symbol is the exact same object as every other #hello symbol.

See "identically equal" section here...
http://sdmeta.gforge.inria.fr/FreeBooks/ByExample/08%20-%20Chapter%206%20-%20Special%20Symbol.pdf

cheers, ben

On Fri, Apr 8, 2016 at 7:20 AM, Valentin Ryckewaert <[hidden email]> wrote:
> Hello everyone,
>
> i'm learning Pharo and i'm having difficulties to understand the
> symbols, what are they? How are they different of the ByteString ? Why
> are they usefull ?
> Why should I put #string where I can put 'string' ?
>
> Thanks in advance for your answer.
> Valentin Ryckewaert

Damien Cassou-2

Re: Pharo-users Question about the symbols

Henrik Nergaard <[hidden email]> writes:

> | s1 s2 |
>
> s1 := 1234 asString.
> s2 := 1234 asString.
>
> s1 = s2. "true"
> s1 == s2. "false"
>
> s1 asSymbol = s2 asSymbol. "true"
> s1 asSymbol == s2 asSymbol. "true"
>
> (s1 class allInstances select: [:s | s = s1 ]) size. "2"
> (s1 asSymbol class allInstances select: [:s | s = s1 asSymbol ]) size. "1"
>
> [ #stringA = #stringB ] bench. "26,812,864 per second"
> [ 'StringA' = 'StringB' ] bench. "3,492,987 per second"

very very nice summary.

--
Damien Cassou
http://damiencassou.seasidehosting.st

"Success is the ability to go from one failure to another without
losing enthusiasm." --Winston Churchill

Sven Van Caekenberghe-2

Re: Pharo-users Question about the symbols

> On 08 Apr 2016, at 09:19, Damien Cassou <[hidden email]> wrote:
>
> Henrik Nergaard <[hidden email]> writes:
>
>> | s1 s2 |
>>
>> s1 := 1234 asString.
>> s2 := 1234 asString.
>>
>> s1 = s2. "true"
>> s1 == s2. "false"
>>
>> s1 asSymbol = s2 asSymbol. "true"
>> s1 asSymbol == s2 asSymbol. "true"
>>
>> (s1 class allInstances select: [:s | s = s1 ]) size. "2"
>> (s1 asSymbol class allInstances select: [:s | s = s1 asSymbol ]) size. "1"
>>
>> [ #stringA = #stringB ] bench. "26,812,864 per second"
>> [ 'StringA' = 'StringB' ] bench. "3,492,987 per second"
>
> very very nice summary.

YES!

> --
> Damien Cassou
> http://damiencassou.seasidehosting.st
>
> "Success is the ability to go from one failure to another without
> losing enthusiasm." --Winston Churchill

stepharo

Re: Pharo-users Question about the symbols

In reply to this post by Damien Cassou-2

>> | s1 s2 |
>>
>> s1 := 1234 asString.
>> s2 := 1234 asString.
>>
>> s1 = s2. "true"
>> s1 == s2. "false"
>>
>> s1 asSymbol = s2 asSymbol. "true"
>> s1 asSymbol == s2 asSymbol. "true"
>>
>> (s1 class allInstances select: [:s | s = s1 ]) size. "2"
>> (s1 asSymbol class allInstances select: [:s | s = s1 asSymbol ]) size. "1"
>>
>> [ #stringA = #stringB ] bench. "26,812,864 per second"
>> [ 'StringA' = 'StringB' ] bench. "3,492,987 per second"
> very very nice summary.
>

CyrilFerlicot

Re: Pharo-users Question about the symbols

In reply to this post by Henrik Nergaard

On 08/04/2016 09:05, Henrik Nergaard wrote:

Hi Henrik,

The class comment of Symbol is really not enough. It need improvement. I
think it would be good to add your examples at least in the class comment.

--
Cyril Ferlicot

http://www.synectique.eu

165 Avenue Bretagne
Lille 59000 France

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stepharo

Re: Pharo-users Question about the symbols

Good idea!

Stef

Le 8/4/16 09:49, Cyril Ferlicot Delbecque a écrit :

>
> On 08/04/2016 09:05, Henrik Nergaard wrote:
>> | s1 s2 |
>>
>> s1 := 1234 asString.
>> s2 := 1234 asString.
>>
>> s1 = s2. "true"
>> s1 == s2. "false"
>>
>> s1 asSymbol = s2 asSymbol. "true"
>> s1 asSymbol == s2 asSymbol. "true"
>>
>> (s1 class allInstances select: [:s | s = s1 ]) size. "2"
>> (s1 asSymbol class allInstances select: [:s | s = s1 asSymbol ]) size. "1"
>>
>> [ #stringA = #stringB ] bench. "26,812,864 per second"
>> [ 'StringA' = 'StringB' ] bench. "3,492,987 per second"
>>
>> Best regards,
>> Henrik
> Hi Henrik,
>
> The class comment of Symbol is really not enough. It need improvement. I
> think it would be good to add your examples at least in the class comment.
>