Call string substitution "substitution" instead of "interpolation". As Shane

pointed out, interpolation is a bad name for this, since it implies something
different.

doc/ZConfig/zconfig.tex

@@ -507,10 +507,10 @@ This module provides a single function:
 \end{funcdesc}
 
 
-\section{\module{ZConfig.Interpolation} --- String interpolation}
+\section{\module{ZConfig.Substitution} --- String substitution}
 
-\declaremodule{}{ZConfig.Interpolation}
-\modulesynopsis{Shell-style string interpolation helper}
+\declaremodule{}{ZConfig.Substitution}
+\modulesynopsis{Shell-style string substitution helper}
 
 This module provides a basic substitution facility similar to that
 found in the Bourne shell (\program{sh} on most \UNIX{} platforms).  
@@ -543,40 +543,40 @@ For these functions, the \var{mapping} argument can be a \class{dict},
 or any type that supports the \method{get()} method of the mapping
 protocol.
 
-\begin{funcdesc}{interpolate}{s, mapping}
-  Interpolate values from \var{mapping} into \var{s}.  Replacement
+\begin{funcdesc}{substitute}{s, mapping}
+  Substitute values from \var{mapping} into \var{s}.  Replacement
   values are copied into the result without further interpretation.
-  Raises \exception{InterpolationSyntaxError} if there are malformed
+  Raises \exception{SubstitutionSyntaxError} if there are malformed
   constructs in \var{s}.
 \end{funcdesc}
 
 \begin{funcdesc}{get}{mapping, name\optional{, default}}
-  Return the value for \var{name} from \var{mapping}, interpolating
+  Return the value for \var{name} from \var{mapping}, replacing
   values recursively if needed.  If \var{name} cannot be found in
   \var{mapping}, \var{default} is returned without being
-  interpolated.
-  Raises \exception{InterpolationSyntaxError} if there are malformed
-  constructs in \var{s}, or \exception{InterpolationRecursionError} if
+  replaced.
+  Raises \exception{SubstitutionSyntaxError} if there are malformed
+  constructs in \var{s}, or \exception{SubstitutionRecursionError} if
   any name expands to include a reference to itself either directly or
   indirectly.
 \end{funcdesc}
 
 The following exceptions are defined:
 
-\begin{excdesc}{InterpolationError}
-  Base class for errors raised by the \module{ZConfig.Interpolation}
+\begin{excdesc}{SubstitutionError}
+  Base class for errors raised by the \module{ZConfig.Substitution}
   module.  Instances provide the attributes \member{message} and
   \member{context}.  \member{message} contains a description of the
   error.  \member{context} is either \code{None} or a list of names
-  that have been looked up in the case of nested interpolation.
+  that have been looked up in the case of nested substitution.
 \end{excdesc}
 
-\begin{excdesc}{InterpolationSyntaxError}
-  Raised when interpolation source text contains syntactical errors.
+\begin{excdesc}{SubstitutionSyntaxError}
+  Raised when the source text contains syntactical errors.
 \end{excdesc}
 
-\begin{excdesc}{InterpolationRecursionError}
-  Raised when a nested interpolation is recursive.  The
+\begin{excdesc}{SubstitutionRecursionError}
+  Raised when a nested substitution is recursive.  The
   \member{context} attribute will always be a list for this
   exception.  An additional attribute, \member{name}, gives the name
   for which an recursive reference was detected.
@@ -585,18 +585,18 @@ The following exceptions are defined:
 
 \subsection{Examples}
 
-These examples show how \function{get()} and \function{interpolate()}
+These examples show how \function{get()} and \function{substitute()}
 differ.
 
 \begin{verbatim}
->>> from ZConfig.Interpolation import get, interpolate
+>>> from ZConfig.Substitution import get, substitute
 >>> d = {'name': 'value',
 ...      'top': '$middle',
 ...      'middle' : 'bottom'}
 >>>
->>> interpolate('$name', d)
+>>> substitute('$name', d)
 'value'
->>> interpolate('$top', d)
+>>> substitute('$top', d)
 '$middle'
 >>>
 >>> get(d, 'name')