{"id":559,"date":"2023-08-21T08:49:50","date_gmt":"2023-08-21T08:49:50","guid":{"rendered":"https:\/\/concordant-thought.com\/?page_id=559"},"modified":"2023-08-21T08:49:50","modified_gmt":"2023-08-21T08:49:50","slug":"pm-2003-02","status":"publish","type":"page","link":"https:\/\/concordant-thought.com\/personal\/robert\/pm-2003-02\/","title":{"rendered":"pm-2003-02"},"content":{"rendered":"<p><span style=\"color: #000000;\">for DC Perl Mongers, 4 February 2003<\/span><\/p>\n<table width=\"100%\">\n<tbody>\n<tr>\n<td align=\"center\"><span style=\"color: #000000;\"><b>Documentation<\/b><\/span><\/td>\n<td align=\"center\"><span style=\"color: #000000;\"><b>Code<\/b><\/span><\/td>\n<td align=\"center\"><span style=\"color: #000000;\"><b>Samples<\/b><\/span><\/td>\n<\/tr>\n<tr>\n<td valign=\"top\">\n<ul>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/ElementMap.status.html\" target=\"_blank\" rel=\"noopener\">ElementMap.status<\/a>: Main documentation<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/Layered.status.html\" target=\"_blank\" rel=\"noopener\">Layered.status<\/a>: simple docs for the Hash::Layered module<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/Driver.pod.html\" target=\"_blank\" rel=\"noopener\">Driver.pod<\/a>: Token docs for driver<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/Grove.pod.html\" target=\"_blank\" rel=\"noopener\">Grove.pod<\/a>: Token docs for driver<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/SGMLS.pod.html\" target=\"_blank\" rel=\"noopener\">SGMLS.pod<\/a>: Token docs for driver<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/XMLParser.pod.html\" target=\"_blank\" rel=\"noopener\">XMLParser.pod<\/a>: Token docs for driver<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/Project.status.html\" target=\"_blank\" rel=\"noopener\">Project.status<\/a>: Notes rom past and future<\/span><\/li>\n<\/ul>\n<\/td>\n<td valign=\"top\">\n<ul>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/ElementMap.pm.html\" target=\"_blank\" rel=\"noopener\">ElementMap.pm<\/a>: The main module object<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/Layered.pm.html\" target=\"_blank\" rel=\"noopener\">Layered.pm<\/a>: The stack-hash data structure<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/test_pl.html\" target=\"_blank\" rel=\"noopener\">test.pl<\/a>: main test code<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/layered-test_pl.html\" target=\"_blank\" rel=\"noopener\">layered-test.pl<\/a>: Hash::Layered specific tests<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/Driver.pm.html\" target=\"_blank\" rel=\"noopener\">Driver.pm<\/a>: the Driver base class (does little)<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/Grove.pm.html\" target=\"_blank\" rel=\"noopener\">Grove.pm<\/a>: the Grove driver (it\u2019s the simplest of the drivers because it has the whole document in memory as a tree)<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/EventQueue.pm.html\" target=\"_blank\" rel=\"noopener\">EventQueue.pm<\/a>: common base class for the event drivers: SGMLS and XMLParser<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/SGMLS.pm.html\" target=\"_blank\" rel=\"noopener\">SGMLS.pm<\/a>: the SGMLSpm driver<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/XMLParser.pm.html\" target=\"_blank\" rel=\"noopener\">XMLParser.pm<\/a>: the XML::Parser::Expat driver (has to be expat because it feeds the document through piecewise in order to get control back from the parsing. it isn\u2019t supposed to be pretty)<\/span><\/li>\n<\/ul>\n<\/td>\n<td rowspan=\"2\" valign=\"top\">\n<ul>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/identity.pm.html\" target=\"_blank\" rel=\"noopener\">identity.pm<\/a>: implementation of code to output a document just as it was input. This shows accessing of all the parser data you can get<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/identity-run.html\" target=\"_blank\" rel=\"noopener\">identity-run<\/a>: command to actually run the identity.pm module<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/calc.pm.html\" target=\"_blank\" rel=\"noopener\">calc.pm<\/a>: implementation of the simple calculator example<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/calc-run.html\" target=\"_blank\" rel=\"noopener\">calc-run<\/a>: command to actually run the calc.pm code<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/calc.dtd.txt\" target=\"_blank\" rel=\"noopener\">calc.dtd<\/a>: The DTD for the simple calculator document<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/test-simple.calc.txt\" target=\"_blank\" rel=\"noopener\">test-simple.calc<\/a>: input document for the simple calculator example<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/test-simple.calc-out.txt\" target=\"_blank\" rel=\"noopener\">test-simple.calc-out<\/a>: output for running the simple calculator on the test-simple.calc document<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/trace-calc-1.txt\" target=\"_blank\" rel=\"noopener\">trace-calc-1<\/a>: output for running the simple calculator on the test-simple.calc document with calc\u2019s debug tracing<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/trace-calc-2.txt\" target=\"_blank\" rel=\"noopener\">trace-calc-2<\/a>: output for running the simple calculator on the test-simple.calc document with debug tracing activee for calc.pm and SGML::ElementMap<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/trace-calc-3.txt\" target=\"_blank\" rel=\"noopener\">trace-calc-3<\/a>: output for running the simple calculator on the test-simple.calc document with debug tracing for all of calc.pm, SGML::ElementMap and Hash::Layered<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/desc2dtd_pl.html\" target=\"_blank\" rel=\"noopener\">desc2dtd.pl<\/a>: older file for generating a DTD from a DTD description document (like a simple XMLSchema)<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/htmltrans.html\" target=\"_blank\" rel=\"noopener\">htmltrans<\/a>: older but substantial example for formatting ASM International article documents into HTML<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/character-old.pm.html\" target=\"_blank\" rel=\"noopener\">character-old.pm<\/a>: an old formatting script showing a different style of interacting with the parser (which is still better than directly managing the parser events)<\/span><\/li>\n<li><span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/http:\/\/concordantthought.com\/personal\/robert\/pm-2003-02\/samples\/character-new.pm.html\" target=\"_blank\" rel=\"noopener\">character-new.pm<\/a>: the modern version of the above script<\/span><\/li>\n<\/ul>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"2\"><span style=\"color: #000000;\">If you are looking at these on your own, you\u2019ll need to understand that several of the samples files refer to older versions of this module, even all the way back to its original incarnation as a helper built on SGML::SPGrove (which is now XML::Grove). The main differences are in accessing the parsed data, but there are some cosmetic changes here and there (and of course inability to use newer capabilities).<\/span><\/p>\n<p><span style=\"color: #000000;\">You can get the SGML::ElementMap module and its respective submodules, examples and documentation from\u00a0<a style=\"color: #000000;\" href=\"https:\/\/web.archive.org\/web\/20220525141829\/https:\/\/web.archive.org\/web\/20040825003728\/https:\/\/www.concordant-thought.com\/personal\/robert\/relay\/\">this directory<\/a>. Don\u2019t forget to get the highest version. That directory also contains these notes and files compressed into a single archive.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><span style=\"color: #000000;\">Mention:<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">the core value of SGML is in being able to make changes to the script for mass changes to documents<\/span>\n<ul>\n<li><span style=\"color: #000000;\">The htmltrans script reliably converts the ASM Handbook Series (23 volumes, 2,000 articles, 22,000 pages, 37,000 images, 10,000 tables) to crosslinked html with tables of contents, etc.<\/span><\/li>\n<li><span style=\"color: #000000;\">This seperation is also useful on even very small scales, because it guarantees consistency and leads to increased reliability.<\/span><\/li>\n<\/ul>\n<\/li>\n<li><span style=\"color: #000000;\">this module predates XSLT<\/span><\/li>\n<li><span style=\"color: #000000;\">doing\/allowing things several different ways to give flexibility to use\/develop a variety of idioms<\/span>\n<ul>\n<li><span style=\"color: #000000;\">maybe some of that potential doesn\u2019t pan out, can tighten up later<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<hr \/>\n<p><span style=\"color: #000000;\">The processing model<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">hierarchical code, like the document structure<\/span><\/li>\n<li><span style=\"color: #000000;\">keep code together and intuitive, especially for pre-content, post-content<\/span><\/li>\n<\/ul>\n<p><span style=\"color: #000000;\">A code sample for OmniMark and ElementMap. This fragment takes elements from \u201c<code>&lt;ext.xref pointer='ARTICLE_ID'&gt;content&lt;\/ext.xref&gt;<\/code>\u201d to \u201c<code>&lt;ext.xref vol.no='NUM' collection='NUM'&gt;content&lt;\/ext.xref&gt;<\/code>\u201d<\/span><\/p>\n<pre><span style=\"color: #000000;\"><code>\r\n;; omnimark code\r\nelement ext.xref\r\n  local counter junk\r\n    and stream volnum\r\n    and stream colnum\r\n    and switch successful\r\n  output \"&lt;%lq\"\r\n  repeat over specified attributes as spec-attr\r\n    output \" \"\r\n    output key of attribute spec-attr\r\n    output \"=%\"%hv(spec-attr)%\"\"\r\n  again\r\n  activate successful\r\n  reset junk to system-call \"%g(idcommand) --format='vol.no=%%v col.no=%%c' --save-output=%g(TempFile) %v(pointer)\"\r\n  do unless file \"%g(TempFile)\" exists\r\n    deactivate successful\r\n    put #error \"Warning: auto-generated file %g(TempFile) not found%n\"\r\n    increment ErrorCount\r\n  else\r\n    do scan file \"%g(TempFile)\"\r\n      match \"vol.no=\" (letter or digit)+ =&gt; vol white-space+ \"col.no=\" (letter or digit)+ =&gt; col\r\n         set buffer volnum to \"%x(vol)\"\r\n         set buffer colnum to \"%x(col)\"\r\n      else\r\n        deactivate successful\r\n        put #error \"Warning: auto-generated file %g(TempFile) is invalid: [%v(pointer)]%n\"\r\n        increment ErrorCount\r\n    done\r\n    ;reset junk to system-call \"rm %g(TempFile)\"\r\n  done\r\n  do when not active successful\r\n    set buffer volnum to \"unknown\"\r\n    set buffer colnum to \"unknown\"\r\n  done\r\n  output \" vol.no=%\"%g(volnum)%\" collection=%\"%g(colnum)%\"\"\r\n  output \"&gt;%c\"\r\n  output \"\"\r\n<\/code><\/span><\/pre>\n<p><span style=\"color: #000000;\">Omnimark<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">has good sgml parsing and support built in<\/span><\/li>\n<li><span style=\"color: #000000;\">has rough equivalent of Data::Locations<\/span><\/li>\n<li><span style=\"color: #000000;\">looks really awful (even worse than perl!)<\/span><\/li>\n<li><span style=\"color: #000000;\">lacks major advances in programming language design, like functions<\/span><\/li>\n<li><span style=\"color: #000000;\">actually, has improved a lot<\/span>\n<ul>\n<li><span style=\"color: #000000;\">less pointlessly verbose<\/span><\/li>\n<li><span style=\"color: #000000;\">functions<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<pre><span style=\"color: #000000;\"><code>\r\n# this is just thrown together from the omnimark code: there might be errors\r\n$e-&gt;element('EXT.XREF', sub {\r\n    my ($engine, $element) = @_;\r\n    my ($attrs, $successful, $line, $volnum, $colnum);\r\n    $output-&gt;print(\"&lt;\".$element-&gt;{'Name'}.\" \");\r\n    $attrs = $element-&gt;{'Attributes'}\r\n    foreach (@$attrs) {\r\n        $output-&gt;print(\" \" . $_ . '=\"' . $attrs-&gt;{$_} . '\"');\r\n    }\r\n    system($idcommand, \"--format='vol.no=%v col.no=%c'\",\r\n           \"--save-output=\".$TempFile, $attrs-&gt;{'pointer'});\r\n  OK: {\r\n      $successful = 0;\r\n      if (! -f $TempFile) {\r\n          warn \"Warning: auto-generated file \".$TempFile.\" not found\\n\";\r\n          $ErrorCount += 1;\r\n          last OK;\r\n      }\r\n      $line = &lt;$TempFile&gt;;\r\n      if ($line &amp;&amp; $line =~ m\/vol\\.no=(\\w+)\\s+col\\.no=(\\w+)\/) {\r\n          $volnum = $1;\r\n          $colnum = $2;\r\n      } else {\r\n          warn \"Warning: auto-generated file \" . $TempFile .\r\n              \" is invalid: [\" . $attrs-&gt;{'pointer'} . \"]\\n\";\r\n          $ErrorCount += 1;\r\n          last OK;\r\n      }\r\n      $successful = 1;\r\n  }\r\n    if (!$successful) {\r\n        $volnum = $colnum = 'unknown';\r\n    }\r\n    $output-&gt;print(' vol.no=\"'.$volnum.'\" collection=\"'.$colnum.'\"&gt;');\r\n    $engine-&gt;process_content;\r\n    $output-&gt;print(\"{'Name'}.\"&gt;\");\r\n});\r\n<\/code><\/span><\/pre>\n<p><span style=\"color: #000000;\">Other processors<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">impossible with PerlSAX<\/span>\n<ul>\n<li><span style=\"color: #000000;\">SAX calls you, so you MUST return from a start element handler before you will get any content events, and the content and end element handlers are called at the same level as the start handler<\/span><\/li>\n<li><span style=\"color: #000000;\">you have to track ALL the document state and your own to-do<\/span><\/li>\n<li><span style=\"color: #000000;\">Note this is only a problem because Perl lacks threads<\/span>\n<ul>\n<li><span style=\"color: #000000;\">Java encourages threads, so these were natural decisions for SAX<\/span><\/li>\n<li><span style=\"color: #000000;\">but bad decisions for PerlSAX<\/span><\/li>\n<li><span style=\"color: #000000;\">pull vs push<\/span>\n<ul>\n<li><span style=\"color: #000000;\">an event pull API can be translated into a push API<\/span><\/li>\n<li><span style=\"color: #000000;\">reverse requires threads to partition the parsing from the processing call hierarchy<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<li><span style=\"color: #000000;\">XSLT<\/span>\n<ul>\n<li><span style=\"color: #000000;\">if you want to be able to program in it, then you should use a programming language<\/span>\n<ul>\n<li><span style=\"color: #000000;\">pointless reinvention fragments progress<\/span><\/li>\n<li><span style=\"color: #000000;\">convolutes programmatic processing with static processing<\/span><\/li>\n<li><span style=\"color: #000000;\">discourages development of good style engines and models<\/span><\/li>\n<li><span style=\"color: #000000;\">discourages development of good hooks and API in above too<\/span><\/li>\n<\/ul>\n<\/li>\n<li><span style=\"color: #000000;\">came after my module anyway<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<hr \/>\n<p><span style=\"color: #000000;\">Should read the SGML::ElementMap documentation and start looking at the ElementMap.pm code<\/span><\/p>\n<p><span style=\"color: #000000;\">Why use constants for object data reference?<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">obvious, less important: speed (hash lookups much slower than arrays)<\/span><\/li>\n<li><span style=\"color: #000000;\">less obvious, more important: correctness (no name typos, no subclass name conflicts, actual name space separation)<\/span><\/li>\n<li><span style=\"color: #000000;\">see code for subclass creation (eg Driver::SGMLS)<\/span><\/li>\n<\/ul>\n<p><span style=\"color: #000000;\">What do we do with handlers?<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">store them in bunches by handler type<\/span><\/li>\n<li><span style=\"color: #000000;\">need to keep ordering for handlers that might match<\/span><\/li>\n<li><span style=\"color: #000000;\">seperate into two cases: default handlers and name handlers<\/span>\n<ul>\n<li><span style=\"color: #000000;\">use hash and \u201d as name for default handlers<\/span><\/li>\n<li><span style=\"color: #000000;\">only need to keep order under a name and among default handlers<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><span style=\"color: #000000;\">What do the main objects look like? (Notice the colons. This is kind of structure describing pseudo-perl. Nothing formal or correct.)<\/span><\/p>\n<pre><span style=\"color: #000000;\"><code>\r\nmode : {\r\n  'handler_type' =&gt; handler_set : {\r\n          'NAME' or '' =&gt; handler_pair : [ pattern, handler_ref ]\r\n\r\n$mode = { '_ MODENAME ' =&gt; 'FOO',\r\n          '_ FINALIZE ' =&gt; '',\r\n          'Element' =&gt; {\r\n              'PARA' =&gt; [ '.*\/SECTION\/.*', \\\u00a7ion;_para ],\r\n              '' =&gt; [ '', \\&amp;no;_handler_warning ] },\r\n          'CData' =&gt; {\r\n              '' =&gt; [ '', \\&amp;data;_accumulate ] },\r\n      };\r\n<\/code><\/span><\/pre>\n<p><span style=\"color: #000000;\">Mode<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">mode has its name saved in it<\/span><\/li>\n<li><span style=\"color: #000000;\">current modes is just a list of refs to modes, need to recover names<\/span><\/li>\n<li><span style=\"color: #000000;\">modes could easily be arrays<\/span><\/li>\n<li><span style=\"color: #000000;\">generally use hashes early on<\/span>\n<ul>\n<li><span style=\"color: #000000;\">trivial to mix around data fields<\/span><\/li>\n<li><span style=\"color: #000000;\">might want transient fields<\/span><\/li>\n<li><span style=\"color: #000000;\">later if the fields are static, convert to arrays<\/span><\/li>\n<\/ul>\n<\/li>\n<li><span style=\"color: #000000;\">finalize field has ref to lookup proc and data if mode is finalized $finalized_data =&gt; [ \\&amp;lookup;_func, $handler1, $handler2, \u2026 ]<\/span><\/li>\n<\/ul>\n<pre><span style=\"color: #000000;\"><code>\r\n$main = [\r\n     $state_data,\r\n     $all_modes,\r\n     $global_vars,\r\n     $stack_vars\r\n ];\r\n\r\n$state_data = [\r\n     driver : SGML::ElementMap::Driver\r\n     node_path : ''\r\n     handler_modes : [ $mode, $mode_2, $mode_3, ... ]\r\n     handler_mode_stack : [ $mode_set_1, $mode_set_2, ... ]\r\n     named_handlers : { 'NAME' =&gt; \\&amp;handler; }\r\n     last_gen_name : 'aaa'\r\n ];\r\n\r\n$all_modes = { 'MODE_NAME_1' =&gt; $mode,\r\n               'MODE_NAME_2' =&gt; $mode_2 };\r\n\r\n$global_vars = { 'NAME' =&gt; $some_value };\r\n\r\n$stack_vars = Hash::Layered;\r\n<\/code><\/span><\/pre>\n<p><span style=\"color: #000000;\">Why global variable support?<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">might simplify cases where handlers cross packages and only the ElementMap object itself is reliably common to all modules. Imagine processing with many interchangeable modules of handlers<\/span><\/li>\n<li><span style=\"color: #000000;\">that\u2019s not really necessary, probably remove soon<\/span><\/li>\n<\/ul>\n<p><span style=\"color: #000000;\">Why stack variable support?<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">need to collect and manage data along the doc hierarchy, just like with code<\/span>\n<ul>\n<li><span style=\"color: #000000;\">otherwise handlers will have problems when they are their own children<\/span><\/li>\n<\/ul>\n<\/li>\n<li><span style=\"color: #000000;\">technically local() is good enough, but have had many troubles with local()<\/span><\/li>\n<li><span style=\"color: #000000;\">the special modes for layers add some extra possibility<\/span><\/li>\n<li><span style=\"color: #000000;\">maybe should not have this hardwired into the processing: hooks instead<\/span><\/li>\n<\/ul>\n<h1><span style=\"color: #000000;\">Drivers<\/span><\/h1>\n<p><span style=\"color: #000000;\">Different processors need different interfaces to work with them<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">the core data is the same, as is the structure<\/span><\/li>\n<li><span style=\"color: #000000;\">in-memory vs serialized vs parsing quality\/detail<\/span><\/li>\n<\/ul>\n<pre><span style=\"color: #000000;\"><code>\r\n# these can default to Driver methods\r\n$d-&gt;input($type);  # 'file' 'literal' 'handle' etc.\r\n$d-&gt;markup($type); # 'xml' or 'sgml'\r\n$d-&gt;parser($parser_object);\r\n$d-&gt;process_xml_file($elementmap, $file, @handler_args);\r\n$d-&gt;process_sgml_file($elementmap, $file, @handler_args);\r\n# these must be implemented in Driver sub-classes\r\n$d-&gt;process(...);\r\n$d-&gt;reparent_current_subtree($new_el_name, @attribute_pairss);\r\n$d-&gt;reparent_subtree($new_el_name, @attribute_pairss);\r\n$d-&gt;dispatch_subtrees($elementmap, $pattern, @handler_args);\r\n$d-&gt;skip_subtrees();\r\n$d-&gt;context_path();\r\n<\/code><\/span><\/pre>\n<p><span style=\"color: #000000;\">Some of the drivers have a lot in common: the simple event based ones. So we have Driver::EventQueue<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">maintains a control stack and a parse event queue<\/span><\/li>\n<li><span style=\"color: #000000;\">the event queue is filled by calling the actual driver\u2019s queue_more_events method<\/span><\/li>\n<li><span style=\"color: #000000;\">the control stack says what to do with events in the event queue<\/span>\n<ul>\n<li><span style=\"color: #000000;\">need to notice when the current element closes<\/span><\/li>\n<li><span style=\"color: #000000;\">reparenting requires insertion of synthesized events at the right places<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<hr \/>\n<h1><span style=\"color: #000000;\">Hash::Layered<\/span><\/h1>\n<p><span style=\"color: #000000;\">Sample execution:<\/span><\/p>\n<pre><span style=\"color: #000000;\"><code>\r\n$h-&gt;set_default('cascade');\r\n$h-&gt;{'a'} = 31;\r\n$h-&gt;{'b'} = 32;\r\n$h-&gt;{'c'} = 33;\r\n$h-&gt;push;\r\n<\/code><\/span><\/pre>\n<table border=\"1\">\n<tbody>\n<tr>\n<td><span style=\"color: #000000;\">cascade<\/span><\/td>\n<td><span style=\"color: #000000;\">a<\/span><\/td>\n<td><span style=\"color: #000000;\">b<\/span><\/td>\n<td><span style=\"color: #000000;\">c<\/span><\/td>\n<td><span style=\"color: #000000;\">d<\/span><\/td>\n<td><span style=\"color: #000000;\">e<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"color: #000000;\">default<\/span><\/td>\n<td><span style=\"color: #000000;\">31<\/span><\/td>\n<td><span style=\"color: #000000;\">32<\/span><\/td>\n<td><span style=\"color: #000000;\">33<\/span><\/td>\n<td><\/td>\n<td><\/td>\n<\/tr>\n<tr>\n<td><span style=\"color: #000000;\">default<\/span><\/td>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<pre><span style=\"color: #000000;\"><code>\r\nassert($h-&gt;{'a'} == 31);\r\n$h-&gt;set_layer('opaque');\r\nassert(! defined $h-&gt;{'a'});\r\n$h-&gt;{'c'} = 34;\r\n$h-&gt;{'d'} = 35;\r\n<\/code><\/span><\/pre>\n<table border=\"1\">\n<tbody>\n<tr>\n<td><span style=\"color: #000000;\">cascade<\/span><\/td>\n<td><span style=\"color: #000000;\">a<\/span><\/td>\n<td><span style=\"color: #000000;\">b<\/span><\/td>\n<td><span style=\"color: #000000;\">c<\/span><\/td>\n<td><span style=\"color: #000000;\">d<\/span><\/td>\n<td><span style=\"color: #000000;\">e<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"color: #000000;\">default<\/span><\/td>\n<td><span style=\"color: #000000;\">31<\/span><\/td>\n<td><span style=\"color: #000000;\">32<\/span><\/td>\n<td><span style=\"color: #000000;\">33<\/span><\/td>\n<td><\/td>\n<td><\/td>\n<\/tr>\n<tr>\n<td><span style=\"color: #000000;\">opaque<\/span><\/td>\n<td><\/td>\n<td><\/td>\n<td><span style=\"color: #000000;\">34<\/span><\/td>\n<td><span style=\"color: #000000;\">35<\/span><\/td>\n<td><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<pre><span style=\"color: #000000;\"><code>\r\n$h-&gt;set_layer('default')\r\nassert($h-&gt;{'a'} == 31);\r\nassert($h-&gt;{'b'} == 32);\r\nassert($h-&gt;{'c'} == 34);\r\nassert($h-&gt;{'d'} == 35);\r\n$h-&gt;push;\r\n$h-&gt;{'a'} = 36\r\n$h-&gt;set_layer('oneway');\r\n$h-&gt;{'e'} = 37\r\n$h-&gt;{'a'} = 38\r\n<\/code><\/span><\/pre>\n<table border=\"1\">\n<tbody>\n<tr>\n<td><span style=\"color: #000000;\">cascade<\/span><\/td>\n<td><span style=\"color: #000000;\">a<\/span><\/td>\n<td><span style=\"color: #000000;\">b<\/span><\/td>\n<td><span style=\"color: #000000;\">c<\/span><\/td>\n<td><span style=\"color: #000000;\">d<\/span><\/td>\n<td><span style=\"color: #000000;\">e<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"color: #000000;\">default<\/span><\/td>\n<td><span style=\"color: #000000;\">36<\/span><\/td>\n<td><span style=\"color: #000000;\">32<\/span><\/td>\n<td><span style=\"color: #000000;\">33<\/span><\/td>\n<td><\/td>\n<td><\/td>\n<\/tr>\n<tr>\n<td><span style=\"color: #000000;\">default<\/span><\/td>\n<td><\/td>\n<td><\/td>\n<td><span style=\"color: #000000;\">34<\/span><\/td>\n<td><span style=\"color: #000000;\">35<\/span><\/td>\n<td><\/td>\n<\/tr>\n<tr>\n<td><span style=\"color: #000000;\">oneway<\/span><\/td>\n<td><span style=\"color: #000000;\">38<\/span><\/td>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<td><span style=\"color: #000000;\">37<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<pre><span style=\"color: #000000;\"><code>\r\nassert $h-&gt;{'a'} == 38\r\nassert $h-&gt;{'b'} == 32\r\nassert $h-&gt;{'e'} == 37\r\n$h-&gt;pop\r\nassert !defined $h-&gt;{'e'}\r\n$h-&gt;pop\r\nassert $h-&gt;{'a'} 36\r\nassert $h-&gt;{'b'} 32\r\nassert $h-&gt;{'c'} 33\r\nassert !defined $h-&gt;{'d'}\r\n<\/code><\/span><\/pre>\n<p><span style=\"color: #000000;\">Want to use the object as a hash reference, but still have access to object methods. I initially tried this with a single object; however, that did not work. I don\u2019t have notes, unfortunately, but I think the issue was getting the data structure out to work with. Using a single object, it\u2019s more difficult to tell when a method is called if it needs to call tied (note that the hash ref and the object ref will be blessed to the same object, so ref() won\u2019t help). Using two objects makes this very easy.<\/span><\/p>\n<p><span style=\"color: #000000;\">(Note: Haven\u2019t converted to use sub constants for object fields.)<\/span><\/p>\n<p><span style=\"color: #000000;\">Have two places for behavior settings<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">individual layer<\/span><\/li>\n<li><span style=\"color: #000000;\">\u201cdefault\u201d<\/span>\n<ul>\n<li><span style=\"color: #000000;\">used when the layer has \u201cdefault\u201d semantics<\/span><\/li>\n<li><span style=\"color: #000000;\">lets you change behavior easily for most of the layers<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><span style=\"color: #000000;\">Layers have IDs<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">combined from an id in the layer_data_list and the layer_data_count<\/span><\/li>\n<li><span style=\"color: #000000;\">lets us reuse layer_data_list arrays<\/span><\/li>\n<li><span style=\"color: #000000;\">we don\u2019t actually use them for anything, they are more to catch errors<\/span><\/li>\n<\/ul>\n<p><span style=\"color: #000000;\"><code>intervening_layer($target_index, $is_write)<\/code><\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">key internal function<\/span><\/li>\n<li><span style=\"color: #000000;\">searches for an opaque layer between the current layer and the target_index<\/span><\/li>\n<li><span style=\"color: #000000;\">target_index can be \u2018top\u2019<\/span><\/li>\n<li><span style=\"color: #000000;\">$is_write is 0 for read, 1 for write, and 2 for a new key<\/span><\/li>\n<li><span style=\"color: #000000;\">should use a cache, but I haven\u2019t put it in<\/span>\n<ul>\n<li><span style=\"color: #000000;\">fancy behaviors mean you need seperate caches for reads and writes<\/span><\/li>\n<li><span style=\"color: #000000;\">haven\u2019t done any consideration on the cost of that extra caching<\/span><\/li>\n<\/ul>\n<\/li>\n<li><span style=\"color: #000000;\">note I don\u2019t call _intervening_layer as an object method<\/span>\n<ul>\n<li><span style=\"color: #000000;\">it\u2019s already slow<\/span><\/li>\n<li><span style=\"color: #000000;\">it\u2019s called from everywhere<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><span style=\"color: #000000;\">behaviors for the hash<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">opaque : completely blocks other layers<\/span><\/li>\n<li><span style=\"color: #000000;\">transparent : ignored unless it already has the key<\/span><\/li>\n<li><span style=\"color: #000000;\">hidden : ignored entirely<\/span><\/li>\n<li><span style=\"color: #000000;\">oneway : opaque to writes, transparent to reads<\/span><\/li>\n<li><span style=\"color: #000000;\">cascade : opaque to new keys, transparent to existing keys<\/span><\/li>\n<\/ul>\n<p><span style=\"color: #000000;\">OK, OK, how does it work?<\/span><\/p>\n<pre><span style=\"color: #000000;\"><code>\r\n$layered_hash = [\r\n   $default_layer_state : 'cascade'\r\n   $layer_data_count : -1\r\n   $layer_data_list : [ $layer_data_1, $layer_data_2, ... ]\r\n   $var_val_stack_hash : { }\r\n   $iter_data : [ [ keys], key_index, intervening_layer_for_reads]\r\n];\r\n\r\n$layer_data = [\r\n   $sub_id,\r\n   $behavior,\r\n   'VAR1',   # list of all variables that have values in this layer\r\n   'VAR2',\r\n   ...\r\n];\r\n\r\n$var_val_stack_hash = {\r\n  'VAR1' =&gt; [ $layer_index_1, $val_1,  $layer_index_2, $val_2,  ... ]\r\n  ...\r\n};\r\n<\/code><\/span><\/pre>\n<p><span style=\"color: #000000;\">Huh?<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">each layer has an id, a behavior, and a list of variable keys<\/span><\/li>\n<li><span style=\"color: #000000;\">each variable key (NOT LAYER) has<\/span>\n<ul>\n<li><span style=\"color: #000000;\">a list of pairs: a layer index and a value<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><span style=\"color: #000000;\">Lookup of a key<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">find the key in the var_val_stack_hash<\/span><\/li>\n<li><span style=\"color: #000000;\">get last two elements: layer index and value<\/span><\/li>\n<li><span style=\"color: #000000;\">see if there is an opaque layer between the current layer and the one with the value<\/span><\/li>\n<\/ul>\n<p><span style=\"color: #000000;\">Iteration<\/span><\/p>\n<ul>\n<li><span style=\"color: #000000;\">get a list of all keys<\/span><\/li>\n<li><span style=\"color: #000000;\">lookup intervening opaque layer for reads<\/span><\/li>\n<li><span style=\"color: #000000;\">skip any keys blocked by the opaque layer<\/span><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>for DC Perl Mongers, 4 February 2003 Documentation Code Samples ElementMap.status: Main documentation Layered.status: simple docs for the Hash::Layered module Driver.pod: Token docs for driver Grove.pod: Token docs for driver SGMLS.pod: Token docs for driver XMLParser.pod: Token docs for driver Project.status: Notes rom past and future ElementMap.pm: The main module object Layered.pm: The stack-hash data [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":544,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"_links":{"self":[{"href":"https:\/\/concordant-thought.com\/wp-json\/wp\/v2\/pages\/559"}],"collection":[{"href":"https:\/\/concordant-thought.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/concordant-thought.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/concordant-thought.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/concordant-thought.com\/wp-json\/wp\/v2\/comments?post=559"}],"version-history":[{"count":3,"href":"https:\/\/concordant-thought.com\/wp-json\/wp\/v2\/pages\/559\/revisions"}],"predecessor-version":[{"id":563,"href":"https:\/\/concordant-thought.com\/wp-json\/wp\/v2\/pages\/559\/revisions\/563"}],"up":[{"embeddable":true,"href":"https:\/\/concordant-thought.com\/wp-json\/wp\/v2\/pages\/544"}],"wp:attachment":[{"href":"https:\/\/concordant-thought.com\/wp-json\/wp\/v2\/media?parent=559"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}