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+History of Cheetah
+==================
+
+(history)
+
+In Spring 2001, several members of the webware-discuss mailing list
+expressed the need for a template engine. Webware like Python is
+great for organizing logic, but they both suffer when you need to
+do extensive variable interpolation into large pieces of text, or
+to build up a text string from its nested parts. Python's {%}
+operator gets you only so far, the syntax is cumbersome, and you
+have to use a separate format string for each nested part. Most of
+us had used template systems from other platforms-chiefly Zope's
+DTML, PHPLib's Template object and Java's Velocity-and wanted to
+port something like those so it could be used both in Webware
+servlets and in standalone Python programs.
+
+Since I (Mike Orr) am writing this history, I'll describe how I
+encountered Cheetah. I had written a template module called
+PlowPlate based on PHPLib's Template library. Like PHPLib, it used
+regular expressions to search and destroy-er, replace-placeholders,
+behaved like a dictionary to specify placeholder values, contained
+no directives, but did have BEGIN and END markers which could be
+used to extract a named block (subtemplate). Meanwhile, Tavis Rudd
+was also on webware-discuss and interested in templates, and he
+lived just a few hours away. So on 12 May 2001 we met in Vancouver
+at a gelato shop on Denman Street and discussed Webware, and he
+drew on a napkin the outline of a template system he was working
+on.
+
+[Note from Tavis: Mikes got the dates and sequence of things a
+little out of order, but what the hell ...]
+
+Instead of filling the template by search-and-replace, he wanted to
+break it up into parts. This was a primitive form of template
+compiling: do the time-consuming work once and put it to a state
+where you can fill the template quickly multiple times. A template
+without directives happens to break down naturally into a list of
+alternating text/placeholder pairs. The odd subscript values are
+literal strings; the even subscripts are string keys into a
+dictionary of placeholder values. The project was called
+TemplateServer.
+
+In a couple months, Tavis decided that instead of compiling to a
+list, he wanted to compile to Python source code: a series of
+{write} calls that would output into a file-like object. This was
+the nucleus that became Cheetah. I thought that idea was stupid,
+but it turned out that this not-so-stupid idea blew all the others
+out of the water in terms of performance.
+
+Another thing Tavis pushed hard for from near the beginning was
+"display logic", or simple directives like {#for}, {#if} and
+{#echo}. (OK, {#echo} came later, but conceptually it belongs here.
+I thought display logic was even stupider than compiling to Python
+source code because it would just lead to "DTML hell"-complicated
+templates that are hard to read and maintain, and for which you
+have to learn (and debug) a whole new language when Python does it
+just fine. But others (hi Chuck!) had templates that were
+maintained by secretaries who didn't know Python, and the
+secretaries needed display logic, so that was that. Finally, after
+working with Cheetah templates (with display logic) and PlowPlate
+templates (with just blocks rather than display logic), I realized
+Tavis was smarter than I was and display logic really did belong in
+the template.
+
+The next step was making directives for all the Python flow-control
+statements: {#while}, {#try}, {#assert}, etc. Some of them we
+couldn't think of a use for. Nevertheless, they were easy to code,
+and "somebody" would probably need them "someday", so we may as
+well implement them now.
+
+During all this, Chuck Esterbrook, Ian Bicking and others offered
+(and still offer) their support and suggestions, and Chuck gave us
+feedback about his use of Cheetah-its first deployment in a
+commercial production environment. Later, Edmund Lian became our #1
+bug reporter and suggester as he used Cheetah in his web
+applications.
+
+We were going to release 1.0 in January 2002, but we decided to
+delay it until more people used it in real-world situations and
+gave us feedback about what is still needed. This has led to many
+refinements, and we have added (and removed) features according to
+this feedback. Nevertheless, Cheetah has been changing but stable
+since the late-binding rewrite in fall 2001, and anybody who keeps
+up with the cheetah-discuss mailing list will know when changes
+occur that require modifying one's template, and since most people
+use point releases rather than CVS, they generally have a few
+week's warning about any significant changes.
+
+More detail on Cheetah's history and evolution, and why it is the
+way it is, can be found in our paper for the Python10 conference,
+http://www.cheetahtemplate.org/Py10.html.
+
+