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Add the %extra_context directive to lemon, as an alternative to %extra_argument.

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Use this to improve the performance of the parser.

FossilOrigin-Name: be47a6f5262a43f477700579512fe7112a0872faedcbbe5c3383d13a08af6440
This commit is contained in:
drh
2018-04-21 13:51:42 +00:00
parent f3d7bbb767
commit fb32c44e41
8 changed files with 125 additions and 56 deletions
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doc/lemon.html
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@ -99,6 +99,9 @@ Show only the basis for each parser state in the report file.
<li><b>-c</b>
Do not compress the generated action tables. The parser will be a
little larger and slower, but it will detect syntax errors sooner.
<li><b>-d</b><i>directory</i>
Write all output files into <i>directory</i>. Normally, output files
are written into the directory that contains the input grammar file.
<li><b>-D<i>name</i></b>
Define C preprocessor macro <i>name</i>. This macro is usable by
"<tt><a href='#pifdef'>%ifdef</a></tt>" and
@ -679,6 +682,30 @@ of type "MyStruct*" and all action routines will have access to
a variable named "pAbc" that is the value of the 4th parameter
in the most recent call to Parse().</p>
<p>The <tt>%extra_context</tt> directive works the same except that it
is passed in on the ParseAlloc() or ParseInit() routines instead of
on Parse().
<a name='extractx'></a>
<h4>The <tt>%extra_context</tt> directive</h4>
The <tt>%extra_context</tt> directive instructs Lemon to add a 2th parameter
to the parameter list of the ParseAlloc() and ParseInif() functions. Lemon
doesn't do anything itself with these extra argument, but it does
store the value make it available to C-code action routines, destructors,
and so forth. For example, if the grammar file contains:</p>
<p><pre>
%extra_context { MyStruct *pAbc }
</pre></p>
<p>Then the ParseAlloc() and ParseInit() functions will have an 2th parameter
of type "MyStruct*" and all action routines will have access to
a variable named "pAbc" that is the value of that 2th parameter.</p>
<p>The <tt>%extra_argument</tt> directive works the same except that it
is passed in on the Parse() routine instead of on ParseAlloc()/ParseInit().
<a name='pfallback'></a>
<h4>The <tt>%fallback</tt> directive</h4>