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
>
>
>
>
>
