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121 lines
5.4 KiB
OpenEdge ABL
121 lines
5.4 KiB
OpenEdge ABL
How To Include This Module.
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What to do to make use of the syntax module in a new command-line tool.
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@h Status.
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The syntax module provided as one of the "services" suite of modules, which means
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that it was built with a view to potential incorporation in multiple tools.
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It can be found, for example, in //inform7//, //inbuild// and //syntax-test//,
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among others. //syntax-test// may be useful as a minimal example of a tool
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using //syntax//.
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By convention, the modules considered as "services" have no dependencies on
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other modules except for //foundation// and other "services" modules.
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A tool can import //syntax// only if it also imports //foundation// and
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//words//.
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@h Importing the module.
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We'll use the term "parent" to mean the tool which is importing //syntax//,
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that is, which will include its code and be able to use it. As with any
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imported module,
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(*) The contents page of the parent's web must identify and locate the
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module:
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= (text as Inweb)
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Import: somepath/syntax
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=
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(*) The parent must call |SyntaxModule::start()| just after it starts up, and
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|SyntaxModule::end()| just before it shuts down. (But just after, and just
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before, the corresponding calls to //foundation//.)
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But in addition, the parent of //syntax// must define some Preform grammar:
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(*) |<language-modifying-sentence>| to recognise sentences modifying the
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language which is currently being parsed;
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(*) |<structural-sentence>| to recognise structurally important sentences;
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(*) |<dividing-sentence>| to recognise sentences which divide up the text,
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normally headings;
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(*) |<comma-divisible-sentence>| to recognise sentences where a comma plays
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a role normally expected to be played by a colon.
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Though compulsory, these don't need to do much: see //syntax-test: Unit Tests//.
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@h Using callbacks.
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Shared modules like this one are tweaked in behaviour by defining "callback
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functions". This means that the parent might provide a function of its own
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which would answer a question put to it by the module, or take some action
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on behalf of the module: it's a callback in the sense that the parent is
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normally calling the module, but then the module calls the parent back to
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ask for data or action.
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The parent must indicate which function to use by defining a constant with
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a specific name as being equal to that function's name. A fictional example
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would be
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= (text as Inweb)
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@d EXPRESS_SURPRISE_SYNTAX_CALLBACK Emotions::gosh
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=
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void Emotions::gosh(text_stream *OUT) {
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WRITE("Good gracious!\n");
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}
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=
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The syntax module has many callbacks, but they are all optional. The following
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alphabetical list has references to fuller explanations:
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(*) |AMBIGUITY_JOIN_SYNTAX_CALLBACK| can rearrange ambiguous readings as
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added to a syntax tree: see //SyntaxTree::add_reading//.
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(*) |ANNOTATION_COPY_SYNTAX_CALLBACK| can perform deep rather than shallow
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copies of node annotations when these are essential: see //Annotations::copy//.
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(*) |ANNOTATION_PERMISSIONS_SYNTAX_CALLBACK|, |MORE_ANNOTATION_PERMISSIONS_SYNTAX_CALLBACK|
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and |EVEN_MORE_ANNOTATION_PERMISSIONS_SYNTAX_CALLBACK| gives permission for nodes
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of given types to have annotations with given IDs, and effectively provides a
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way to create custom annotations: see //Annotations::make_annotation_allowed_table//.
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(*) |BEGIN_OR_END_HERE_SYNTAX_CALLBACK| is called when a new extension beginning
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or ending sentence is found in the source text being broken into sentences:
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see //Sentences::make_node//.
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(*) |DIVIDE_AT_COLON_SYNTAX_CALLBACK| is called to ask permission to break a
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sentence at a colon. See //Sentences::break_inner//.
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(*) |IS_SENTENCE_NODE_SYNTAX_CALLBACK| is asked whether a given node represents
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a regular sentence or not: see //NodeType::is_sentence//.
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(*) |LANGUAGE_ELEMENT_SYNTAX_CALLBACK| is called when a sentence is found matching
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the nonterminal |<language-modifying-sentence>|: see //Sentences::make_node//.
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(*) |LOG_UNENUMERATED_NODE_TYPES_SYNTAX_CALLBACK| is called to log a node type
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not recognised as one of the enumerated |*_NT| values: see //NodeType::log//.
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(*) |NEW_HEADING_SYNTAX_CALLBACK| is called when a new heading sentence is found
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in the source text being broken into sentences: see //Sentences::make_node//.
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(*) |NEW_HEADING_TREE_SYNTAX_CALLBACK| is called when a new syntax tree is being
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created, and needs to be given a matching tree of headings: see //SyntaxTree::new//.
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(*) |NODE_METADATA_SETUP_SYNTAX_CALLBACK|, |MORE_NODE_METADATA_SETUP_SYNTAX_CALLBACK|
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and |EVEN_MORE_NODE_METADATA_SETUP_SYNTAX_CALLBACK| adds new syntax tree node
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types: see //NodeType::metadata_setup//.
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(*) |PARENTAGE_EXCEPTIONS_SYNTAX_CALLBACK| allows exceptions to the rules about
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which nodes in a syntax tree can be parents of which other nodes: see
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//NodeType::parentage_allowed//.
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(*) |PARENTAGE_PERMISSIONS_SYNTAX_CALLBACK|, |MORE_PARENTAGE_PERMISSIONS_SYNTAX_CALLBACK|
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and |EVEN_MORE_PARENTAGE_PERMISSIONS_SYNTAX_CALLBACK| adds permissions for nodes
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to be parents of each other: see //NodeType::make_parentage_allowed_table//.
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(*) |PROBLEM_SYNTAX_CALLBACK| is called when a syntax error is found, and can
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prevent this from being issued to the terminal as an error message: see
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//Sentences::syntax_problem//.
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(*) |NEW_NONSTRUCTURAL_SENTENCE_SYNTAX_CALLBACK| is called when a new, regular
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sentence is found in the source text being broken into sentences: see
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//Sentences::make_node//.
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(*) |UNKNOWN_PREFORM_RESULT_SYNTAX_CALLBACK| is used only by the Preform cache:
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if this isn't being used, it's sufficient to return a null pointer. See
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//Simple Preform Cache//.
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