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RE: [xml-dev] RE: Declarative programming requires a differentmindset

On Sun, 2010-04-11 at 08:27 -0400, Michael Sokolov wrote:
> Postscript is an interesting case - I am told that it is Turing-complete,
> but its uses are almost entirely declarative: for layout, akin to HTML.
> Perhaps someone more knowledgeable about PS on this list would care to
> comment on how that came to be?

PostScript is a procedural graphics language that uses a reverse polish
notation to manipulate a stack. Yes, it's Turing-complete, or as
complete as one can get with finite memory :-) PostScript is nothing
whatsoever like HTML -- here's a simple example:

/Times-Italic findfont % search the font dictionary for Times-Italic
18 scalefont           % scale the font to 18pt
setfont                % make it the current font
72 72 moveto           % Move to 1 inch from the top left of the page
(Hello World)          % push a string "Hello World" onto the stack
show                   % render the string in 18pt Times Italic
showpage               % print the current page and clear the buffer

Hope this helps.


Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://fromoldbooks.org/
Ankh: irc.sorcery.net irc.gnome.org www.advogato.org

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