April 2016 - Pharo-users - lists.pharo.org

Re: [Pharo-users] Pharo-users Question about the symbols

by Damien Cassou

Henrik Nergaard <henrik.nergaard(a)uia.no> 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

April 8, 2016

Re: [Pharo-users] Pharo-users Question about the symbols

by Henrik Nergaard

| 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:pharo-users-bounces@lists.pharo.org] On Behalf Of Ben Coman Sent: Friday, April 8, 2016 3:23 AM To: Any question about pharo is welcome <pharo-users(a)lists.pharo.org> 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-%… cheers, ben On Fri, Apr 8, 2016 at 7:20 AM, Valentin Ryckewaert <valentin.ryckewaert(a)gmail.com> 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

April 8, 2016

Re: [Pharo-users] Pharo-users Question about the symbols

by Cyril Ferlicot

On Friday, 8 April 2016, Valentin Ryckewaert <valentin.ryckewaert(a)gmail.com> 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

April 8, 2016

Re: [Pharo-users] Pharo-users Question about the symbols

by Brad Selfridge

And symbols are immutable Brad Sent from my iPad > On Apr 7, 2016, at 9:41 PM, Markus Stumptner <mst(a)cs.unisa.edu.au> 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-%… >> >> cheers, ben >> >> On Fri, Apr 8, 2016 at 7:20 AM, Valentin Ryckewaert >> <valentin.ryckewaert(a)gmail.com> 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 > >

April 8, 2016

Re: [Pharo-users] Pharo-users Question about the symbols

by Markus Stumptner

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-%… > > cheers, ben > > On Fri, Apr 8, 2016 at 7:20 AM, Valentin Ryckewaert > <valentin.ryckewaert(a)gmail.com> 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 >

April 8, 2016

Re: [Pharo-users] Pharo-users Question about the symbols

by Ben Coman

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-%… cheers, ben On Fri, Apr 8, 2016 at 7:20 AM, Valentin Ryckewaert <valentin.ryckewaert(a)gmail.com> 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

April 8, 2016

Pharo-users Question about the symbols

by Valentin Ryckewaert

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

April 7, 2016

Re: [Pharo-users] FFI return by reference

by Damien Pollet

I think in that case you need to pass an instance of FFIExternalValueHolder. On 7 April 2016 at 17:42, Thibault Raffaillac <thibault.raffaillac(a)inria.fr> wrote: > Hi again, > > Does anyone know what is the state of return by reference in FFI? > Example: > glGetAttribute: attr into: value > <primitive: #primitiveNativeCall module: #NativeBoostPlugin error: > errorCode> > ^ self nbCall: #( int SDL_GL_GetAttribute(SDL_GLattr attr, int > *value) ) > > On my image (50666) it does nothing on value yet (if nil, remains nil, if > SmallInteger 0, remains 0). > (SDL2 glGetAttribute: 6 into: value) should return 16. > I've seen NBOpenGL put "out" before value in method header, should it > matter? (does not make it work though) > Last but not least, should we attach '*' to the type or variable for FFI > to understand it is a pointer? > > Cheers, > Thibault Raffaillac > >

April 7, 2016

FFI return by reference

by Thibault Raffaillac

Hi again, Does anyone know what is the state of return by reference in FFI? Example: glGetAttribute: attr into: value <primitive: #primitiveNativeCall module: #NativeBoostPlugin error: errorCode> ^ self nbCall: #( int SDL_GL_GetAttribute(SDL_GLattr attr, int *value) ) On my image (50666) it does nothing on value yet (if nil, remains nil, if SmallInteger 0, remains 0). (SDL2 glGetAttribute: 6 into: value) should return 16. I've seen NBOpenGL put "out" before value in method header, should it matter? (does not make it work though) Last but not least, should we attach '*' to the type or variable for FFI to understand it is a pointer? Cheers, Thibault Raffaillac

April 7, 2016

Passing nil with FFI

by Thibault Raffaillac

Hi, I am having trouble passing nil to a function with FFI (i.e. NULL, i.e. 0). For example: SDL2 glCreateContext: nil. The function expects a subclass of FFIExternalObject, so calls instVarAt: 1 but nil has no such field! Am I missing something? (like a special nil instance of FFIExternalObject) Note however that putting nil works when FFI expects a String. Cheers, Thibault Raffaillac

April 7, 2016