Note that any valid SGML or XML document that references an external subset in its DTD, or whose body contains references to parsed external entities declared in its DTD ( including those declared within its internal subset ), may only be partially parsed but cannot be fully validated by validating SGML or XML parsers in their standalone mode ( this means that these validating parsers will not attempt to retrieve these external entities, and their replacement text will not be accessible ).

Notations are also completely opaque for XML and SGML parsers, so they are not differentiated by the type of the external entity that they may reference ( for these parsers they just have a unique name associated to a public identifier ( an FPI ) and / or a system identifier ( a URI )).

The ASCII code for space may not be represented directly because it could cause older parsers to split up the encoded word undesirably.

Abstraction typically includes linguist-directed search but may include e. g., rule-learning for parsers.

Even when they terminate, parsers that use recursive descent with backup may require exponential time.

This means, contrary to LR ( 0 ) parsers, a different action may be executed, if the item to process is followed by a different terminal.

Microsoft Outlook uses a proprietary datastore file and interface which are impossible to read without being parsed, and such parsers may in turn not be able to exist legally without performing reverse engineering.

For the purpose of expression evaluation, the major advantage of eval over expression parsers is that, in most programming environments where is supported, the expression may be arbitrarily complex, and may include calls to functions written by the user that could not have possibly been known in advance by the parser's creator.

For example, XML parsers may intern names of tags and attributes to save memory.

However, such documents will still be fully parsable in the non-standalone mode of validating parsers, which will signal an error if these external entities cannot be located with their specified public identifier ( FPI ) and / or system identifier ( a URI ), or are inaccessible.

( Notations declared in the DTD are also referencing external entities, but these unparsed entities are not needed for the validation of documents in the standalone mode of these parsers: the validation of all external entities referenced by notations is left to the application using the SGML or XML parser ).

This use allows notations to be defined only in a DTD stored as an external entity and referenced only as the external subset of documents, and allows these documents to remain compatible with validating XML or SGML parsers that have no direct support for notations.

Instead, these parsers just provide to the application the parsed FPI and / or URI associated to the notations found in the parsed SGML or XML document, and with a facility for a dictionary containing all notation names declared in the DTD ; these validating parsers will also check the uniqueness of notation name declarations, and will report a validation error if some notation names are used anywhere in the DTD or in the document body but not declared:

Some programs that create IFF files add chunks to them with their internal data ; these same files can later be read by other programs without any disruption ( because their parsers could skip uninteresting chunks ) which is a great advantage of IFF and similar formats.

Moreover, the specifications describing these formats are routinely made available to the public, thus increasing the availability of parsers and emitters across programming languages.

The tokenization is necessary because of the way these parsers use lookahead to parse CFGs that meet certain requirements in linear time.

A parser that exploits these relations is considerably simpler than more general-purpose parsers such as LALR parsers.

And the content of the " img " element is referencing another external entity " example1SVG " whose declaration also does not define an notation, so it will also be parsed by validating parsers and the entity replacement text will be located by its defined SYSTEM identifier " example1. svg " ( also interpreted as a relative URI ).

Note also that even in validating SGML or XML 1. 0 or XML 1. 1 parsers, the external entities referenced by an FPI and / or URI in declared notations are not retrieved automatically by the parsers themselves.

Most XML schema languages are only replacements for element declarations and attribute list declarations, in such a way that it becomes possible to parse XML documents with non-validating XML parsers ( if the only purpose of the external DTD subset was to define the schema ).

It uses external parsers to build documents.

However, the " title " attribute of the " img " element specifies the internal entity " example1SVGTitle " whose declaration that does not define an annotation, so it will be parsed by validating parsers and the entity replacement text will be " Title of example1. svg ".

Some applications ( but not XML or SGML parsers themselves ) also allow referencing notations indirectly by naming them in the < tt >" URN: name "</ tt > value of a standard CDATA attribute, everywhere a URI can be specified.

LALR parsers are automatically generated by compiler compilers such as Yacc and GNU Bison.

LR parsers are mechanically generated from a formal grammar for the language by some parser generator tool.

The above properties of L, R, and k are actually shared by all shift-reduce parsers, including precedence parsers.

As with other shift-reduce parsers, an LR parser works by doing some combination of Shift steps and Reduce steps.

( This accumulative parse stack is very unlike the predictive, leftward-growing parse stack used by top-down parsers.

One of the most noticeable differences between HTML and XHTML is the rule that all tags must be closed: empty HTML tags such as < code >< nowiki ></ nowiki ></ code > must either be closed with a regular end-tag, or replaced by a special form: < code >< nowiki > < nowiki >/></ nowiki ></ code > ( the space before the '< code >< nowiki >/</ nowiki ></ code >' on the end tag is optional, but frequently used because it enables some pre-XML Web browsers, and SGML parsers, to accept the tag ).

Most operator-precedence parsers can be modified to produce postfix expressions ; in particular, once an abstract syntax tree has been constructed, the corresponding postfix expression is given by a simple post-order traversal of that tree.

Such follow sets are also used by generators for LL top-down parsers.

Like most parsers, this parser is automatically generated by compiler compilers like GNU Bison and Menhir.

XML allows parsers to separate the process of interpreting the document syntax and its structure.

This allows parsers to be universal and very light-weight, and to be separated from the process of validating or interpreting the document.

An Earley parser is an example of such an algorithm, while the widely used LR and LL parsers are simpler algorithms that deal only with more restrictive subsets of context-free grammars.

Earley parsers are appealing because they can parse all context-free languages, unlike LR parsers and LL parsers, which are more typically used in compilers but which can only handle restricted classes of languages.

Most languages use separate and different parsers to deal with code and data, Lisp only uses one.

LL ( 1 ) grammars are very popular because the corresponding LL parsers only need to look at the next token to make their parsing decisions.

JSP and Warnier's method both structure programs and data using only sequences, iterations and selections, so they essentially create programs that are parsers for regular expressions which simultaneously match the program's input and output data streams.

EUC, on the other hand, is handled much better by parsers that have been written for 7-bit ASCII ( and thus EUC encodings are used on UNIX, where much of the file-handling code was historically only written for English encodings ).

A metacompiler is not only useful for generating parsers and code generators for domain specific languages, but a metacompiler is also itself a domain-specific language for the domain of compiler writing.

Programmers only need to create events to process the commands rather than syntax parsers.