- regress is a regression testing script,

- *.stx are (mostly arbitrary) reference structured text files, and

- *.ref are previously processed output from the corresponding *.stx files.

Here's the in-depth explanation:

The directory has a bunch of .stx files (ones found on the zope.org
site, plus an 'examples.stx' file, for accumulating a body of
examples) plus corresponding .ref files, previously produced by a
prior, established StructuredText version.  The script 'regress'
applies the new ../StructuredText.py version to produce .new files,
and then compares the .ref files and the .new files, complaining if
any differences are found.

The intended procedure is to make your changes in ../StructuredText.py,
iron them out as best you can, and then try the regress script to
identify any unexpected functionality changes/backwards-compatability
losses.  (We also need to develop the body of reference text and examples.)

lib/python/StructuredText/regressions/Acquisition.stx

+Acquisition
+
+  "Copyright (C) 1996-1998, Digital Creations":COPYRIGHT.html.
+
+  Acquisition [1] is a mechanism that allows objects to obtain
+  attributes from their environment.  It is similar to inheritence,
+  except that, rather than traversing an inheritence hierarchy
+  to obtain attributes, a containment hierarchy is traversed.
+
+  The "ExtensionClass":ExtensionClass.html. release includes mix-in
+  extension base classes that can be used to add acquisition as a
+  feature to extension subclasses.  These mix-in classes use the
+  context-wrapping feature of ExtensionClasses to implement
+  acquisition. Consider the following example::
+
+    import ExtensionClass, Acquisition
+
+    class C(ExtensionClass.Base):
+      color='red'
+
+    class A(Acquisition.Implicit):
+
+      def report(self):
+        print self.color
+
+    a=A()
+    c=C()
+    c.a=A()
+
+    c.a.report() # prints 'red'
+
+    d=C()
+    d.color='green'
+    d.a=a
+
+    d.a.report() # prints 'green'
+
+    a.report() # raises an attribute error
+
+  The class 'A' inherits acquisition behavior from
+  'Acquisition.Implicit'.  The object, 'a', "has" the color of
+  objects 'c' and 'd' when it is accessed through them, but it
+  has no color by itself.  The object 'a' obtains attributes
+  from it's environment, where it's environment is defined by
+  the access path used to reach 'a'.
+
+  Acquisition wrappers
+
+    When an object that supports acquisition is accessed through
+    an extension class instance, a special object, called an
+    acquisition wrapper, is returned.  In the example above, the
+    expression 'c.a' returns an acquisition wrapper that
+    contains references to both 'c' and 'a'.  It is this wrapper
+    that performs attribute lookup in 'c' when an attribute
+    cannot be found in 'a'.
+
+    Aquisition wrappers provide access to the wrapped objects
+    through the attributes 'aq_parent', 'aq_self', 'aq_base'.  
+    In the example above, the expressions::
+      
+       'c.a.aq_parent is c'
+
+    and::
+
+       'c.a.aq_self is a'
+
+    both evaluate to true, but the expression::
+
+       'c.a is a'
+
+    evaluates to false, because the expression 'c.a' evaluates
+    to an acquisition wrapper around 'c' and 'a', not 'a' itself.
+
+    The attribute 'aq_base' is similar to 'aq_self'.  Wrappers may be
+    nested and 'aq_self' may be a wrapped object.  The 'aq_base'
+    attribute is the underlying object with all wrappers removed.
+
+  Acquisition Control
+
+    Two styles of acquisition are supported in the current
+    ExtensionClass release, implicit and explicit aquisition.
+  
+    Implicit acquisition
+    
+      Implicit acquisition is so named because it searches for
+      attributes from the environment automatically whenever an
+      attribute cannot be obtained directly from an object or
+      through inheritence.
+  
+      An attribute may be implicitly acquired if it's name does
+      not begin with an underscore, '_'.
+  
+      To support implicit acquisition, an object should inherit
+      from the mix-in class 'Acquisition.Implicit'.
+  
+    Explicit Acquisition
+  
+      When explicit acquisition is used, attributes are not
+      automatically obtained from the environment.  Instead, the
+      method 'aq_aquire' must be used, as in::
+  
+	print c.a.aq_acquire('color')
+  
+      To support explicit acquisition, an object should inherit
+      from the mix-in class 'Acquisition.Explicit'.
+
+    Controlled Acquisition
+
+      A class (or instance) can provide attribute by attribute control
+      over acquisition.  This is done by:
+
+      - subclassing from 'Acquisition.Explicit', and
+
+      - setting all attributes that should be acquired to the special
+        value: 'Acquisition.Acquired'.  Setting an attribute to this
+        value also allows inherited attributes to be overridden with
+        acquired ones.
+
+	For example, in::
+
+	  class C(Acquisition.Explicit):
+	     id=1
+	     secret=2
+	     color=Acquisition.Acquired
+	     __roles__=Acquisition.Acquired
+
+	The *only* attributes that are automatically acquired from
+	containing objects are 'color', and '__roles__'.  Note also
+	that the '__roles__' attribute is acquired even though it's
+	name begins with an underscore.  In fact, the special
+	'Acquisition.Acquired' value can be used in
+	'Acquisition.Implicit' objects to implicitly acquire selected
+	objects that smell like private objects.
+
+    Filtered Acquisition
+
+      The acquisition method, 'aq_acquire', accepts two optional
+      arguments. The first of the additional arguments is a
+      "filtering" function that is used when considering whether to
+      acquire an object.  The second of the additional arguments is an
+      object that is passed as extra data when calling the filtering
+      function and which defaults to 'None'.
+
+      The filter function is called with five arguments:
+
+      - The object that the 'aq_acquire' method was called on,
+
+      - The object where an object was found,
+
+      - The name of the object, as passed to 'aq_acquire',
+
+      - The object found, and
+
+      - The extra data passed to 'aq_acquire'.
+
+      If the filter returns a true object that the object found is
+      returned, otherwise, the acquisition search continues.
+
+      For example, in::
+
+	from Acquisition import Explicit
+	
+	class HandyForTesting:
+	    def __init__(self, name): self.name=name
+	    def __str__(self):
+		return "%s(%s)" % (self.name, self.__class__.__name__)
+	    __repr__=__str__
+	
+	class E(Explicit, HandyForTesting): pass
+	
+	class Nice(HandyForTesting):
+	    isNice=1
+	    def __str__(self):
+		return HandyForTesting.__str__(self)+' and I am nice!'
+	    __repr__=__str__
+	
+	a=E('a')
+	a.b=E('b')
+	a.b.c=E('c')
+	a.p=Nice('spam')
+	a.b.p=E('p')
+	
+	def find_nice(self, ancestor, name, object, extra):
+	    return hasattr(object,'isNice') and object.isNice
+	
+	print a.b.c.aq_acquire('p', find_nice)
+
+      The filtered acquisition in the last line skips over the first
+      attribute it finds with the name 'p', because the attribute
+      doesn't satisfy the condition given in the filter. The output of
+      the last line is::
+
+        spam(Nice) and I am nice!
+
+  Acquisition and methods
+
+    Python methods of objects that support acquisition can use
+    acquired attributes as in the 'report' method of the first example
+    above.  When a Python method is called on an object that is
+    wrapped by an acquisition wrapper, the wrapper is passed to the
+    method as the first argument.  This rule also applies to
+    user-defined method types and to C methods defined in pure mix-in
+    classes.
+
+    Unfortunately, C methods defined in extension base classes that
+    define their own data structures, cannot use aquired attributes at
+    this time.  This is because wrapper objects do not conform to the
+    data structures expected by these methods.
+
+  Acquiring Acquiring objects
+
+    Consider the following example::
+
+      from Acquisition import Implicit
+      
+      class C(Implicit):
+	  def __init__(self, name): self.name=name
+	  def __str__(self):
+	      return "%s(%s)" % (self.name, self.__class__.__name__)
+	  __repr__=__str__
+      
+      a=C("a")
+      a.b=C("b")
+      a.b.pref="spam"
+      a.b.c=C("c")
+      a.b.c.color="red"
+      a.b.c.pref="eggs"
+      a.x=C("x")
+
+      o=a.b.c.x
+
+    The expression 'o.color' might be expected to return '"red"'. In
+    earlier versions of ExtensionClass, however, this expression
+    failed.  Acquired acquiring objects did not acquire from the
+    environment they were accessed in, because objects were only
+    wrapped when they were first found, and were not rewrapped as they
+    were passed down the acquisition tree.
+
+    In the current release of ExtensionClass, the expression "o.color"
+    does indeed return '"red"'.
+
+    When searching for an attribute in 'o', objects are searched in
+    the order 'x', 'a', 'b', 'c'. So, for example, the expression,
+    'o.pref' returns '"spam"', not '"eggs"'.  In earlier releases of
+    ExtensionClass, the attempt to get the 'pref' attribute from 'o'
+    would have failed.
+
+    If desired, the current rules for looking up attributes in complex
+    expressions can best be understood through repeated application of
+    the '__of__' method:
+
+    'a.x' -- 'x.__of__(a)'
+
+    'a.b' -- 'b.__of__(a)'
+
+    'a.b.x' -- 'x.__of__(a).__of__(b.__of__(a))'
+
+    'a.b.c' -- 'c.__of__(b.__of__(a))'
+
+    'a.b.c.x' --
+        'x.__of__(a).__of__(b.__of__(a)).__of__(c.__of__(b.__of__(a)))'
+
+    and by keeping in mind that attribute lookup in a wrapper
+    is done by trying to lookup the attribute in the wrapped object
+    first and then in the parent object.  In the expressions above
+    involving the '__of__' method, lookup proceeds from left to right.
+
+    Note that heuristics are used to avoid most of the repeated
+    lookups. For example, in the expression: 'a.b.c.x.foo', the object
+    'a' is searched no more than once, even though it is wrapped three
+    times.
+
+.. [1] Gil, J., Lorenz, D., 
+   "Environmental Acquisition--A New Inheritance-Like Abstraction Mechanism",
+   http://www.bell-labs.com/people/cope/oopsla/Oopsla96TechnicalProgramAbstracts.html#GilLorenz, 
+   OOPSLA '96 Proceedings, ACM SIG-PLAN, October, 1996
+	 

lib/python/StructuredText/regressions/examples.ref

+<h1>Small Trials for Structured Text Formatting</h1>
+<p>  This paragraph should be preceded by a level 1 header.  It should
+  not, itself, be made into a header, just a regular paragraph.</p>
+
+<p>  Here are a few presentation styles, in a list <a href="#1">[1]</a>:</p>
+
+<ul><li><p>A word: <em>emphasized</em>.</p>
+
+
+<li><p>A word: <u>underlined</u>.</p>
+
+
+<li><p>A word <strong>strong</strong>.</p>
+
+</ul>
+<p>  .. <a href="#1">[1]</a> (The referring text should be a paragraph, not a header, and
+  should contain a reference to this footnote, footnote "[1]".)</p>
+
+<p>  Some hrefs, in a definition list:</p>
+
+<dl><dt>  <u>Regular</u><dd><p><a href="http://www.zope.org">http://www.zope.org/</a></p>
+
+
+<dt>  <u>W/trailing punctuation</u><dd><p><a href="http://www.zope.org">http://www.zope.org/</a>.</p>
+
+
+<dt>  <u>W protocol implicit</u><dd><p><a href="locallink">locallink</a></p>
+
+
+<dt>  <u>W protocol implicit</u>, alternate<dd><p><a href="locallink">locallink</a>
+</p>
+
+</dl>
+
+

lib/python/StructuredText/regressions/examples.stx

+Small Trials for Structured Text Formatting
+
+  This paragraph should be preceded by a level 1 header.  It should
+  not, itself, be made into a header, just a regular paragraph.
+
+  Here are a few presentation styles, in a list [1]:
+
+  - A word: *emphasized*.
+
+  - A word: _underlined_.
+
+  - A word **strong**.
+
+  .. [1] (The referring text should be a paragraph, not a header, and
+  should contain a reference to this footnote, footnote "[1]".)
+
+  Some hrefs, in a definition list:
+
+  _Regular_ -- "http://www.zope.org/":http://www.zope.org
+
+  _W/trailing punctuation_ -- "http://www.zope.org/":http://www.zope.org.
+
+  _W protocol implicit_ -- "locallink"::locallink
+
+  _W protocol implicit_, alternate -- "locallink", :locallink

lib/python/StructuredText/regressions/index.ref

+<p>
+Extension Class</p>
+<p>    <a href="COPYRIGHT.html">Copyright (C) 1996-1998, Digital Creations</a>.</p>
+
+<p>    A lightweight mechanism has been developed for making Python
+    extension types more class-like.  Classes can be developed in an
+    extension language, such as C or C++, and these classes can be
+    treated like other python classes:</p>
+
+<ul><li><p>They can be sub-classed in python,</p>
+
+
+<li><p>They provide access to method documentation strings, and</p>
+
+
+<li><p>They can be used to directly create new instances.</p>
+
+</ul>
+<p>    Extension classes provide additional extensions to class and
+    instance semantics, including:</p>
+
+<ul><li><p>A protocol for accessing subobjects "in the context of" their
+      containers.  This is used to implement custom method types
+      and <a href="Acquisition.html">environmental acquisition</a>.</p>
+
+
+<li><p>A protocol for overriding method call semantics.  This is used
+      to implement "synchonized" classes and could be used to
+      implement argument type checking.</p>
+
+
+<li><p>A protocol for class initialization that supports execution of a
+      special <code>__class_init__</code> method after a class has been
+      initialized.</p>
+
+</ul>
+<p>    Extension classes illustrate how the Python class mechanism can be
+    extended and may provide a basis for improved or specialized class
+    models. </p>
+
+<h1>Releases</h1>
+<p>    The current release is <a href="ExtensionClass-1.2.tar.gz">1.2</a>
+    To find out what's changed in this release,
+    see the <a href="release.html">release notes</a>.</p>
+
+<p>    Documentation is available <a href="ExtensionClass.html">on-line</a>.</p>
+
+
+<h1>Windows Binaries</h1>
+<p>    A win32 binary release, <a href="ec12.zip">ec12.zip</a> is available.  This
+    release includes all of the ExtensionClass modules built as 
+    Windows extension modules (.pyd) files.  These were built for
+    Python 1.5.1 using Microsoft Visual C++ 5.0 in "Release" mode.</p>
+
+
+<p></p>
+
+
+

lib/python/StructuredText/regressions/index.stx

+
+Extension Class
+  
+    "Copyright (C) 1996-1998, Digital Creations":COPYRIGHT.html.
+
+    A lightweight mechanism has been developed for making Python
+    extension types more class-like.  Classes can be developed in an
+    extension language, such as C or C++, and these classes can be
+    treated like other python classes:
+  
+    - They can be sub-classed in python,
+  
+    - They provide access to method documentation strings, and
+  
+    - They can be used to directly create new instances.
+  
+    Extension classes provide additional extensions to class and
+    instance semantics, including:
+
+    - A protocol for accessing subobjects "in the context of" their
+      containers.  This is used to implement custom method types
+      and "environmental acquisition":Acquisition.html.
+
+    - A protocol for overriding method call semantics.  This is used
+      to implement "synchonized" classes and could be used to
+      implement argument type checking.
+
+    - A protocol for class initialization that supports execution of a
+      special '__class_init__' method after a class has been
+      initialized. 
+  
+    Extension classes illustrate how the Python class mechanism can be
+    extended and may provide a basis for improved or specialized class
+    models. 
+
+  Releases
+
+    The current release is "1.2":ExtensionClass-1.2.tar.gz,
+    To find out what's changed in this release,
+    see the "release notes":release.html.
+
+    Documentation is available "on-line":ExtensionClass.html.
+
+  Windows Binaries
+
+    A win32 binary release, "ec12.zip":ec12.zip, is available.  This
+    release includes all of the ExtensionClass modules built as 
+    Windows extension modules (.pyd) files.  These were built for
+    Python 1.5.1 using Microsoft Visual C++ 5.0 in "Release" mode.
+
+    
+

lib/python/StructuredText/regressions/regress

+#!/bin/bash
+
+# Compare current StructuredText.py processing against prior versions.
+# You should see no output if there's no discrepancies.
+
+for i in *.stx; do
+  stx=$i
+  base=${i%.stx}
+  ref=$base.ref
+  new=$base.new
+  python ../StructuredText.py $stx > $new
+  if cmp $ref $new; then
+    :
+  else
+    echo ... so there are differences in the processing
+  fi
+done