tok.t | documentation |
#charset "us-ascii"
/*
* Tokenizer - customizable tokenizer class for use with the intrinsic
* class 'grammar-production' parser.
*
* This tokenizer implementation is parameterized with a set of rules
* (see below); a basic set of rules is provided, but users can
* customize the tokenizer quite extensively simply by subclassing the
* Tokenizer class and overriding the 'rules_' property with a new set
* of rules declarations.
*/
#include "tads.h"
#include "t3.h"
#include "dict.h"
#include "tok.h"
#include "vector.h"
/* ------------------------------------------------------------------------ */
/*
* Tokenizer exceptions
*/
/*
* base class for all tokenizer errors (to allow blanket 'catch')
*/
class TokenizerError: Exception
displayException() { "Tokenizer exception"; }
;
/*
* no match for token
*/
class TokErrorNoMatch: TokenizerError
construct(str)
{
/* remember the full remaining text */
remainingStr_ = str;
/*
* for convenience, separately remember the single character
* that we don't recognize - this is simply the first character
* of the rest of the line
*/
curChar_ = str.substr(1, 1);
}
displayException()
{ "Tokenizer error: unexpected character '<<curChar_>>'"; }
/*
* The remainder of the string. This is the part that couldn't be
* matched; we were successful in matching up to this point.
*/
remainingStr_ = nil
/* current character (first character of remainingStr_) */
curChar_ = nil
;
/* ------------------------------------------------------------------------ */
/*
* Basic token types
*/
/* word */
enum token tokWord;
/* quoted string */
enum token tokString;
/* punctuation */
enum token tokPunct;
/* integer number */
enum token tokInt;
/* ------------------------------------------------------------------------ */
/*
* Tokenizer base class
*/
class Tokenizer: object
/*
* Tokenizing rules. The subclass can override this to specify a
* list that defines different tokenization rules. Each entry in the
* master rules_ list is one rule. Each rule is a list consisting of
* the name of the rule; the pattern to match for the rule; the token
* type (an 'enum token') to use when the rule is matched; the value
* computation rule; and the value test rule.
*
* The name of a rule is just an arbitrary string to identify the
* rule. This can be used to insert new rules in order relative to
* known existing rules, or to delete known existing rules.
*
* If the value computation rule is nil, we'll just use the matching
* text as the token value. If the value rule is a string, we'll use
* the string as a replacement pattern (with rexReplace). If it's a
* property ID, we'll invoke the property of self with the following
* arguments:
*
* txt, typ, toks
*
* 'txt' is the matched text; 'typ' is the token type from the rule;
* and 'toks' is a vector to which the new token or tokens are to be
* added. The routine is responsible for adding the appropriate
* values to the result list. Note that the routine can add more
* than one token to the results if desired.
*
* If the value test rule is non-nil, it must be either a method or a
* function; we'll call the method or function to test to see if the
* matched value is valid. We'll call the method (on self) with the
* matching text as the argument; if the method returns true, the
* rule matches, otherwise the rule fails, and we'll continue looking
* for another rule as though we hadn't matched the rule's regular
* expression in the first place. This can be used for rules that
* require more than a simple regular expression match; for example,
* the value test can be used to look up the match in a dictionary,
* so that the rule only matches tokens that are defined in the
* dictionary.
*/
rules_ = static
[
/* skip whitespace */
['whitespace', R'<Space>+', nil, &tokCvtSkip, nil],
/* certain punctuation marks */
['punctuation', R'[.,;:?!]', tokPunct, nil, nil],
/*
* Words - note that we convert everything to lower-case. A
* word must start with an alphabetic character, but can contain
* alphabetics, digits, hyphens, and apostrophes after that.
*/
['word', R'<Alpha>(<AlphaNum>|[-\'])*', tokWord, &tokCvtLower, nil],
/* strings */
['string single-quote', R'\'(.*)\'', tokString, nil, nil],
['string double-quote', R'"(.*)"', tokString, nil, nil],
/* integer numbers */
['integer', R'[0-9]+', tokInt, nil, nil]
]
/*
* Insert a new rule before or after the existing rule with the name
* 'curName'. If 'curName' is nil, or rule is found with the given
* name, we'll insert the new rule at the end of the list. 'rule'
* must be a list with the standard elements for a tokenizer rule.
* 'after' is nil to insert the new rule before the given existing
* rule, true to insert after it.
*/
insertRule(rule, curName, after)
{
local idx;
/*
* if the name of an existing rule was supplied, find the
* existing rule with the given name
*/
idx = nil;
if (curName != nil)
idx = rules_.indexWhich({x: tokRuleName(x) == curName});
/* if we didn't find curName, insert at the end of the list */
if (idx == nil)
idx = rules_.length();
/* if we're inserting after the given element, adjust the index */
if (after)
++idx;
/* insert the new rule */
insertRuleAt(rule, idx);
}
/*
* Insert a rule at the given index in our rules list. 'rule' must
* be a list with the standard elements for a tokenizer rule. 'idx'
* is the index of the new rule; we'll insert before the existing
* element at this index; so if 'idx' is 1, we'll insert before the
* first existing rule.
*/
insertRuleAt(rule, idx)
{
/* insert the rule */
rules_ = rules_.insertAt(idx, rule);
}
/*
* Delete a rule by name. This finds the rule with the given name
* and removes it from the list.
*/
deleteRule(name)
{
local idx;
/* find the rule with the given name */
idx = rules_.indexWhich({x: tokRuleName(x) == name});
/* if we found the named element, remove it from the list */
if (idx != nil)
deleteRuleAt(idx);
}
/* delete the rule at the given index */
deleteRuleAt(idx)
{
/* delete the rule */
rules_ = rules_.removeElementAt(idx);
}
/* convert a string to lower-case (for value computation rules) */
tokCvtLower(txt, typ, toks)
{
/* add the lower-cased version of the string to the result list */
toks.append([txt.toLower(), typ, txt]);
}
/*
* processing routine to skip a match - this is used for whitespace
* and other text that does not result in any tokens in the result
* list
*/
tokCvtSkip(txt, typ, toks)
{
/* simply skip the text without generating any new tokens */
}
/*
* Tokenize a string. If we find text that we can't match to any of
* the rules, we'll throw an exception (TokErrorNoMatch). If we
* succeed in tokenizing the entire string, we'll return a list with
* one element per token. Each element of the main list is a
* sublist with the following elements describing a token:
*
* - The first element gives the token's value.
*
* - The second element the token type (given as a token type enum
* value).
*
* - The third element the original token strings, before any
* conversions or evaluations were performed. For example, this
* maintains the original case of strings that are lower-cased for
* the corresponding token values.
*/
tokenize(str)
{
local toks = new Vector(32);
local startIdx = 1;
local len = str.length();
/* keep going until we run out of string */
mainLoop:
while (startIdx <= len)
{
/* run through the rules in sequence until we match one */
ruleLoop:
for (local i = 1, local cnt = rules_.length() ; i <= cnt ; ++i)
{
local cur;
local match;
local val;
/* get the current rule */
cur = rules_[i];
/* check for a match to the rule's pattern */
match = rexMatch(tokRulePat(cur), str, startIdx);
if (match != nil && match > 0)
{
local test;
local txt;
local typ;
/* get the matching text */
txt = str.substr(startIdx, match);
/*
* if there's a value test, invoke it to determine
* if the token really matches
*/
if ((test = tokRuleTest(cur)) != nil)
{
local accept;
/* check what kind of test function we have */
switch (dataType(test))
{
case TypeFuncPtr:
case TypeObject:
/* it's a function or anonymous function */
accept = (test)(txt);
break;
case TypeProp:
/* it's a method */
accept = self.(test)(txt);
break;
default:
/* consider anything else to be accepted */
accept = true;
break;
}
/*
* if the value test failed, it means that the
* token doesn't match this rule after all -
* ignore the regex match and keep searching for
* another rule
*/
if (!accept)
continue ruleLoop;
}
/* get the type of the token from the rule */
typ = tokRuleType(cur);
/* get this value processing rule */
val = tokRuleVal(cur);
/* determine what value to use */
switch(dataTypeXlat(val))
{
case TypeNil:
/* use the matching text verbatim */
toks.append([txt, typ, txt]);
break;
case TypeProp:
/*
* invoke the property - it's responsible for
* adding the token or tokens to the results
* lists
*/
self.(val)(txt, typ, toks);
break;
case TypeSString:
/* it's a regular expression replacement */
toks.append(
[rexReplace(tokRulePat(cur),
txt, val, ReplaceOnce),
typ, txt]);
break;
case TypeFuncPtr:
/* invoke the function */
(val)(txt, typ, toks);
break;
default:
/*
* use any other value exactly as given in
* the rule
*/
toks.append([val, typ, txt]);
break;
}
/*
* continue the search at the next character after
* the end of this token
*/
startIdx += match;
/* start over with the rest of the string */
continue mainLoop;
}
}
/*
* We failed to find a match for this part of the string.
* Throw an exception and let the caller figure out what to
* do. The exception parameter gives the rest of the
* string, so the caller can display a suitable error
* message if desired.
*/
throw new TokErrorNoMatch(str.substr(startIdx));
}
/* we're done with the string - return out value and type lists */
return toks.toList();
}
;
/* ------------------------------------------------------------------------ */
/*
* Test Section
*/
#ifdef TOK_TEST
main(args)
{
"Enter text to tokenize. Type Q or QUIT when done. ";
for (;;)
{
local str, toks;
/* read a string */
"\b>";
str = inputLine();
/* catch tokenization errors */
try
{
/* tokenize the string */
toks = Tokenizer.tokenize(str);
/* if the first token is 'quit', we're done */
if (toks.length() > 0
&& getTokType(toks[1]) == tokWord
&& (getTokVal(toks[1])== 'quit' || getTokVal(toks[1]) == 'q'))
{
/* they want to stop - exit the command loop */
break;
}
/* display the tokens */
for (local i = 1, local cnt = toks.length() ; i <= cnt ; ++i)
"(<<getTokVal(toks[i])>>) ";
}
catch (TokErrorNoMatch err)
{
"Unrecognized punctuation: <<err.remainingStr_.substr(1, 1)>>";
}
}
}
#endif /* TOK_TEST */
TADS 3 Library Manual
Generated on 5/16/2013 from TADS version 3.1.3
Generated on 5/16/2013 from TADS version 3.1.3