gstring.htm

自编的一个String类

particularly the case when <i>WS</i> or <i>OWS</i> terms are present. This needs 
further work. Meanwhile, avoid using <i>LongestString</i> or <i>LDOTS</i> in 
expressions that also include <i>WS</i> or <i>OWS</i>.</p>

<H2><EM><A NAME="TaggedStringList"></A>TaggedStringList</EM> classes</H2>
<P>The <EM>TaggedStringList</EM> family is used to select a subset of the 
StringList for editing. It includes the <EM>TaggedStringList</EM>
class and three classes, <EM>StringList_String</EM>,&nbsp;
<EM>StringList_Range</EM> and <EM>StringList_GString</EM> derived from it.
Objects from these classes are generated from one of the following expressions 
</P>
<PRE>   SL.All()
   SL(string)
   SL(string, string, ends)
   SL(gstring)</PRE>

<P>where <EM>SL</EM> is a StringList,&nbsp; <EM>string</EM> is a String,
<EM>gstring</EM> is a GString, and <EM>ends</EM> is an int. These classes
enable one to edit a subset of the strings in a StringList.</P>
<P><EM>SL.All()</EM> includes <EM>all</EM> the strings in <EM>SL</EM>.</P>
<P><EM>SL(s)</EM>, where <EM>s</EM> is either a character string or an object
of class <EM>String</EM>, includes those strings in <EM>SL</EM> which include
the string <EM>s</EM>.</P>
<P><EM>SL(s1,s2, ends)</EM>, where <EM>s1</EM> and <EM>s2</EM> are either
character strings or objects of class <EM>String</EM>, include those strings in
<EM>SL</EM> selected in the range <EM>s1</EM> to <EM>s2</EM>. The <EM>ends</EM>
parameter, if included, determines which ends of the ranges are included. See
the description in the notes on the <A HREF="#StringList">StringList class</A>.
The default is to include both ends.</P>
<P><EM>SL(gs)</EM>, where <EM>gs</EM> is a <EM>GString</EM> expression,
includes those strings in <EM>SL</EM> which match the pattern <EM>gs</EM>. Note
that here, as elsewhere, the pattern must match the complete string and not
just a subset of it.</P>
<P>Objects of these classes should not be constructed as stand-alone objects
but should be used as part of an editing function such as</P>
<PRE>   SL.All().sa(&quot;target&quot;,&quot;replace with&quot;);</PRE>

<P>They can also the passed to a function as a <EM>TaggedStringList&amp;</EM>
parameter. This provides a way of carrying out more complicated editing
functions that cannot be carried out directly with the functions provided in
TaggedStringList family. These classes can access
<EM>TaggedStringList::iterator</EM> and
<EM>TaggedStringList::reverse_iterator</EM> classes which have the same
properties with corresponding classes associated with the <EM>StringList</EM>
class.</P>
<P><STRONG>Note:</STRONG> do not use the <EM>reverse_iterator</EM> class with a
<EM>StringList_Range</EM> object.</P>

<P><b>Note:</b> if possible, use
a simple string as an argument to <EM>SL</EM> to reduce the number of strings
that have to be searched with a GString.</P>
<H3>The member functions and friends</H3>
<DIV ALIGN="left">
<TABLE BORDER="1" WIDTH="100%" style="border-collapse: collapse" bordercolor="#111111" cellpadding="0" cellspacing="1">
<TR>
<TD WIDTH="50%"><TT>friend ostream&amp; operator&lt;&lt;(ostream&amp; os,
TaggedStringList&amp; tsl);</TT></TD>
<TD WIDTH="50%">Output the entire TaggedStringList to a file.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>iterator begin();</TT></TD>
<TD WIDTH="50%">Return an iterator pointing to the beginning of the
StringList.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>iterator end();</TT></TD>
<TD WIDTH="50%">Return an iterator pointing to one past the end of the
StringList.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>reverse_iterator rbegin();</TT></TD>
<TD WIDTH="50%">Return a reverse iterator pointing to the end of the
StringList.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>reverse_iterator rend();</TT></TD>
<TD WIDTH="50%">Return a reverse iterator pointing one before the beginning of
the StringList.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void erase(iterator i);</TT></TD>
<TD WIDTH="50%">Erase the string corresponding to <EM>i.</EM> See note about
the corresponding entry in the StringList class.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void erase(reverse_iterator i);</TT></TD>
<TD WIDTH="50%">Erase the string corresponding to <EM>i.</EM> See note about
the corresponding entry in the StringList class.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void insert_before(const String&amp; s, iterator
i)</TT></TD>
<TD WIDTH="50%">Insert <EM>s</EM> before the string corresponding to
<EM>i</EM>.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void insert_after(const String&amp; s, iterator
i)</TT></TD>
<TD WIDTH="50%">Insert <EM>s</EM> after the string corresponding to
<EM>i</EM>.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void sf(const String&amp; s1, const String&amp; s2,
iterator i);</TT></TD>
<TD WIDTH="50%">Substitute the first occurrence of <EM>s1</EM> by <EM>s2</EM>
in the string corresponding to <EM>i</EM>.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void sl(const String&amp; s1, const String&amp; s2,
iterator i);</TT></TD>
<TD WIDTH="50%">Substitute the last occurrence of <EM>s1</EM> by <EM>s2</EM> in
the string corresponding to <EM>i</EM>.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void sa(const String&amp; s1, const String&amp; s2,
iterator i);</TT></TD>
<TD WIDTH="50%">Substitute all occurrences of <EM>s1</EM> by <EM>s2</EM> in the
string corresponding to <EM>i</EM>.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void s(GString&amp; g1, GString&amp; g2, iterator
i);</TT></TD>
<TD WIDTH="50%">Substitute the pattern of <EM>g1</EM> by <EM>g2</EM> in the
string corresponding to <EM>i</EM>.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void UpperCase(iterator i);</TT></TD>
<TD WIDTH="50%">Convert the string corresponding to <EM>i</EM> to upper
case.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void LowerCase(iterator i);</TT></TD>
<TD WIDTH="50%">Convert the string corresponding to <EM>i</EM> to lower
case.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void erase();</TT></TD>
<TD WIDTH="50%">Erase all strings selected by the TaggedStringList class.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void insert_before(const String&amp; s)</TT></TD>
<TD WIDTH="50%">Insert <EM>s</EM> before each of the selected strings.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void insert_after(const String&amp; s)</TT></TD>
<TD WIDTH="50%">Insert <EM>s</EM> after each of the selected strings.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void sf(const String&amp; s1, const String&amp;
s2);</TT></TD>
<TD WIDTH="50%">Substitute the first occurrence of <EM>s1</EM> by <EM>s2</EM>
in each of the selected strings.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void sl(const String&amp; s1, const String&amp;
s2);</TT></TD>
<TD WIDTH="50%">Substitute the last occurrence of <EM>s1</EM> by <EM>s2</EM> in
each of the selected strings.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void sa(const String&amp; s1, const String&amp;
s2);</TT></TD>
<TD WIDTH="50%">Substitute all occurrences of <EM>s1</EM> by <EM>s2</EM> in
each of the selected strings.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void s(GString&amp; g1, GString&amp; g2);</TT></TD>
<TD WIDTH="50%">Substitute the pattern of <EM>g1</EM> by <EM>g2</EM> in each of
the selected strings.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void UpperCase();</TT></TD>
<TD WIDTH="50%">Convert the selected strings to upper case.</TD>
</TR>
<TR>
<TD WIDTH="50%"><TT>void LowerCase();</TT></TD>
<TD WIDTH="50%">Convert the selected strings to lower case.</TD>
</TR>
</TABLE>
</DIV>
<P>The iterator versions of the editing functions are intended to be used
within loops involving an iterator. Use a (forward) iterator rather than a
reverse iterator. The editing functions without iterators refer to the whole
TaggedStringList family object.</P>

<H2><A NAME="Examples"></A>Examples</H2>
<P>I have a file, fox.txt, containing the single line:</P>
<PRE>   The quick brown fox jumps over the lazy dog.</PRE>

<P>I demonstrate a variety of statements for editing this line.</P>
<P>Change <EM>quick</EM> to <EM>fast</EM> and print out the resulting line.</P>
<PRE>   ifstream is(&quot;fox.txt&quot;);
   StringList Fox; is &gt;&gt; Fox;
   Fox.All().sa(&quot;quick&quot;, &quot;fast&quot;);
   cout &lt;&lt; Fox;</PRE>

<P>or using GStrings</P>
<PRE>   ifstream is(&quot;fox.txt&quot;);
   StringList Fox; is &gt;&gt; Fox;
   Fox.All().s(DOTS + &quot;quick&quot; + DOTS,
               DOTS + &quot;fast&quot;  + DOTS);
   cout &lt;&lt; Fox;</PRE>

<P>Suppose the fox line is one line in a long file. I want the editing to apply
only to lines that include the word <EM>fox</EM> (where we are ignoring the
possibility that <EM>fox</EM> is included in some other word).</P>
<PRE>   ifstream is(&quot;fox.txt&quot;);
   StringList Fox; is &gt;&gt; Fox;
   Fox(&quot;fox&quot;).s(DOTS + &quot;quick&quot; + DOTS,
                DOTS + &quot;fast&quot;  + DOTS);
   cout &lt;&lt; Fox;</PRE>

<P>I don't know what the adjectives between <EM>The</EM> and <EM>fox</EM> are
but I want to change them to <EM>slow grey</EM>. I show just the editing line. 
</P>
<PRE>   Fox.All().s(GS + &quot;The&quot; + DOTS          + &quot;fox&quot; + DOTS,
                    DOTS  + &quot; slow grey &quot; + DOTS  + DOTS);</PRE>

<P>I am not sure whether the verb is <EM>jump</EM> or <EM>jumps</EM> but I want
to change it to <EM>leap</EM> or <EM>leaps</EM> respectively.</P>
<PRE>   Fox.All().s(DOTS + (GS | &quot;jump&quot; | &quot;jumps&quot;) + DOTS,
               DOTS + (GS | &quot;leap&quot; | &quot;leaps&quot;) + DOTS);</PRE>

<P>I don't what the animals involved are but I want to swap them.</P>
<PRE>   ShortestString SS1, SS2;
   Fox.All().s(GS + &quot;The quick brown &quot; + SS1 + &quot; jumps over the lazy &quot; + SS2 + &quot;.&quot;,
                    DOTS               + SS2 + DOTS                    + SS1 + DOTS);</PRE>

<P>&nbsp;</P>
<H2><A NAME="ToDo"></A>To do</H2>
<P>Operator * to allow multiple copies of a target. I will need three types of
counters <EM>N0</EM> (may be 0 or 1 repetitions), <EM>NN</EM> (may be any
number of repetitions including 0, <EM>N1</EM> (may be any number of
repetitions &gt; 0). Can also have a positive integer. Assume <tt>&gt;</tt> combination
rather than <tt>+</tt>. Assume longest when saying type of <tt>*</tt> expression.&nbsp; This is
going to be a bit of problem as Collect won't work correctly; may need a IntList class to hold switching data.</P>
<P>Review rules regarding shortest and longest.</P>
<P>Rethink handling of white space objects.</P>
<P>Letter by letter translations (SED <EM>y</EM> operator) - need function
R('a', 'z');</P>
<P>Fix problem with <TT>i.erase(); ++i;</TT>. Decide how to handle
<TT>i.insert_next(S); ++i;</TT>.</P>
<P>In TaggedStringList make iterators forward only; make reverse iterator fully
functional (?)</P>
<P>Introduce new editing phase, <EM>Load</EM>, between <EM>Match</EM> and
<EM>Collect</EM> to load values into ShortestString etc. This will ensure value
is not set if not involved in a match. Introduce boolean indicator into
ShortestString etc to show if value has been set; reset when assigned a value
with =. Run <EM>Load</EM> at search stage as well as edit phase.(??)</P>
<P>More internal checking - iterators correctly matched with object they are
accessing, comparisons valid.</P>
<P>Check that operators in collect and translate phases agree.</P>
<P>Notes on implementing new facilities. What is needed for a new
TaggedStringList class and what is needed for a new operator (operator - need
to define action in both GString and InitialGstring; list functions required)
or a new target object. Requirements on Match Load Collect and Translate.
Interchangeable target object <tt>-&gt;</tt> must push one string to list at collect
time and pop one at translate time - note defaults.</P>
<P>Check all target objects are interchangeable between Collect and Translate
phases. Collect must push a value; Translate must Pop a value.</P>
<P>Directory read into StringList - how to handle attributes? </P>
<P>Column oriented input and output</P>
<P>Regular expression input</P>
<P>Number input (eg recognise E format)</P>
<P>Extend and document substitution list facilities </P>
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