2012/7/17 Sven Van Caekenberghe <sven@beta9.be>

Now that I actually read the Wikipedia article, I made the code smaller and more elegant ;-)

String streamContents: [ :stream | | lines |
�� lines := #(
�� 'String streamContents: [ :stream | | lines |'
�� ' �� lines := #('
�� ' �� ).'

�� ' �� (lines first: 2) do: [ :each | stream << each; cr ].'
�� ' �� lines do: [ :each | stream tab: 2; print: each; cr ].'
�� ' �� (lines allButFirst: 2) do: [ :each | stream << each; cr ].'
�� ' �� stream nextPut: $]; cr.'
�� ).
�� (lines first: 2) do: [ :each | stream << each; cr ].
�� lines do: [ :each | stream tab: 2; print: each; cr ].
�� (lines allButFirst: 2) do: [ :each | stream << each; cr ].
�� stream nextPut: $]; cr.
]

On 17 Jul 2012, at 19:03, Sven Van Caekenberghe wrote:

> By accident I visited the following website today
>
> �� http://igoro.com/archive/how-to-write-a-self-printing-program/
>
> It is about writing a self-printing program, also known as a quine
>
> �� http://en.wikipedia.org/wiki/Quine_(computing)
>
> This has probably been done before, but I had to try to do it in Pharo Smalltalk.
> Paste the following in a Workspace and either print or inspect it.
>
> String streamContents: [ :stream | | lines |
> �� lines := #(
> �� 'String streamContents: [ :stream | | lines |'
> �� ' �� lines := #('
> �� ' �� ).'
> �� ' �� stream'
> �� ' �� << ''String streamContents: [ :stream | | lines |''; cr;'
> �� ' �� tab; << ''lines := #(''; cr.'
> �� ' �� lines do: [ :each | stream tab; tab; print: each; cr ].'
> �� ' �� stream tab; << '').''; cr.'
> �� ' �� (lines allButFirst: 3) do: [ :each | stream tab; << each; cr ].'
> �� ' �� stream tab; << '']''; cr.'
> �� ).
> �� stream
> �� << 'String streamContents: [ :stream | | lines |'; cr;
> �� tab; << 'lines := #('; cr.
> �� lines do: [ :each | stream tab; tab; print: each; cr ].
> �� stream tab; << ').'; cr.
> �� (lines allButFirst: 3) do: [ :each | stream tab; << each; cr ].
> �� stream tab; << ']'; cr.
> �� ]
>
> The result _is_ the same, but it is a bit hard to see because String>>#printString renders the printed representation (doubling quotes). To check you can inspect the string and print it on the transcript (after opening it)
>
> �� Transcript show: self
>
> or you can ask the compiler for help
>
> �� Compiler evaluate: self readStream
>
> if you inspect the result of the above expression, you can keep on doing this forever.
>
> It is also pretty easy to extend the example with your own code.
>
> String streamContents: [ :stream | | lines |
> �� lines := #(
> �� 'String streamContents: [ :stream | | lines |'
> �� ' �� lines := #('
> �� ' �� ).'
> �� ' �� stream'
> �� ' �� << ''String streamContents: [ :stream | | lines |''; cr;'
> �� ' �� tab; << ''lines := #(''; cr.'
> �� ' �� lines do: [ :each | stream tab; tab; print: each; cr ].'
> �� ' �� stream tab; << '').''; cr.'
> �� ' �� (lines allButFirst: 3) do: [ :each | stream tab; << each; cr ].'
> �� ' �� stream tab; << '']''; cr.'
> �� ' �� self inform: ''Cool, no ?'''
> �� ).
> �� stream
> �� << 'String streamContents: [ :stream | | lines |'; cr;
> �� tab; << 'lines := #('; cr.
> �� lines do: [ :each | stream tab; tab; print: each; cr ].
> �� stream tab; << ').'; cr.
> �� (lines allButFirst: 3) do: [ :each | stream tab; << each; cr ].
> �� stream tab; << ']'; cr.
> �� self inform: 'Cool, no ?'
> �� ]
>
> Just add the extra code twice.
>
> Enjoy!
>
> Sven
>
>
> --
> Sven Van Caekenberghe
> http://stfx.eu
> Smalltalk is the Red Pill
>
>
>
>
>

--
Bernat Romagosa.