Tokenizer base class

class Tokenizer :   object

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Subclass Tree  


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Summary of Properties  


Summary of Methods  

deleteRule  deleteRuleAt  insertRule  insertRuleAt  tokCvtLower  tokCvtSkip  tokenize 



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.


deleteRule (name)tok.t[195]

Delete a rule by name. This finds the rule with the given name and removes it from the list.

deleteRuleAt (idx)tok.t[208]
delete the rule at the given index

insertRule (rule, curName, after)tok.t[154]
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.

insertRuleAt (rule, idx)tok.t[185]
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.

tokCvtLower (txt, typ, toks)tok.t[215]
convert a string to lower-case (for value computation rules)

tokCvtSkip (txt, typ, toks)tok.t[226]
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

tokenize (str)tok.t[248]
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.

TADS 3 Library Manual
Generated on 5/16/2013 from TADS version 3.1.3