mirror of
https://github.com/pierre42100/comunic
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102 lines
4.0 KiB
Plaintext
Executable File
102 lines
4.0 KiB
Plaintext
Executable File
# parent : Writing-a-language-scanner
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= Writing a simple scanner (with LuminousSimpleScanner) =
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A simple scanner should be used when there are no state-transitions or awkward requirements to worry about.
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For a simple scanner, the basic workflow is this:
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# override `init()`
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# Add tokens using add_pattern
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# If necessary, add overrides for individual tokens using `$this->overrides['TOKEN_NAME'] = function`
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== Completely Automated ==
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Here's a VERY simple and completely automated scanner for a small Python-style language:
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{{{lang=php_snippet
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class MyScanner extends LuminousSimpleScanner {
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function init() {
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$this->add_pattern('COMMENT', '/#.*/');
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$this->add_pattern('STRING', '/"([^\\\\"]+|\\\\.)*("|$)/');
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$this->add_pattern('SHELL_CMD', '/`([^\\\\`]+|\\\\.)*(`|$)/');
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$this->add_pattern('IDENT', '/[a-z_]\w*/');
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$this->add_identifier_mapping('KEYWORD', array('def', 'else', 'elif',
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'for', 'return', 'while'));
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$this->rule_tag_map = array(
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'SHELL_CMD' => 'FUNCTION'
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);
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}
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}
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}}}
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When main() is called, the given tokens will be observed. Simples!
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Notes:
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# Patterns are checked in order. That means the first-defined pattern has precedence if two patterns match (instead of the max-munch-rule).
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# If your given patterns don't fully describe the source code then segments will simply be recorded as a 'null' token.
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# The identifier mappings are a 'filter', which looks at anything recorded as an 'IDENT', and converts them into another token. If you don't specify an 'IDENT' pattern, this has no effect.
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# SHELL_CMD is a made-up token which isn't defined as a CSS class. We use this because it's more readable than calling it some unrelated token name, but we map it to 'FUNCTION' later.
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*Examples*: Java and C# (java.php and csharp.php in languages/)
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== With Overrides==
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Let's say you've got a type that can't be matched by a simple regular expression. For the sake of example we'll use the obvious idea of a '/' as a regex delimiter and a division operator.
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Insert this into your init:
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{{{lang=php_snippet
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class MyScanner extends LuminousSimpleScanner {
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function init() {
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$this->add_pattern('OPERATOR', '@[!%^&*\\\\-=+;:\\|,\\./?]+@');
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$this->add_pattern('SLASH', '%/%'); // special case
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// tokenizing these helps us figure out the slash
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$this->add_pattern('OPENER', '/[\\(\\[\\{]+/');
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$this->add_pattern('CLOSER', '/[\\)\\]\\}]+/');
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//... but they aren't real tokens, as far as highlighting is concerned.
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$this->rule_tag_map['OPENER'] = null;
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$this->rule_tag_map['CLOSER'] = null;
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$this->overrides['SLASH'] = array($this, 'slash_override');
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}
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}
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}}}
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Now, when LuminousSimpleScanner finds it's at the 'SLASH' token, it will stop and call `$this->slash_override`. It expects that function to record and consume some string and will throw an exception if it doesn't (because it would be an infinite loop).
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An override to disambiguate '/' might look something like this:
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{{{lang=php_snippet
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class MyScanner extends LuminousSimpleScanner {
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function slash_override($matches) {
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// to disambiguate it we go backwards over the token array and see what
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// was preceding it.
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$is_regex = false;
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for($i = count($this->tokens)-1; $i >= 0; $i--) {
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// A token is a tuple:
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list($name, $content, $escaped) = $this->tokens[$i];
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if ($t[0] === 'COMMENT' || $t[0] === null)
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continue; // unimportant, ignore
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elseif($t[0] === 'OPERATOR' || $t[0] === 'OPENER')
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$is_regex = true;
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break;
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}
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if ($is_regex) {
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// get and consume the regex pattern
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$str = $this->scan('% / (?> [^\\\\\\\\/]+ | \\\\\\\\.)* ($|/[iogmx]*)%x');
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assert($str !== null); // this must have matched, else our regex is skewy
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$this->record($str, 'REGEX');
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} else {
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$this->record($this->get(), 'OPERATOR');
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}
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}
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}
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}}}
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*Examples*: languages/perl.php is a language which uses several overrides, to handle 'quote-like delimiters', heredoc, and regex/slash disambiguation. |