Provided by: libmarpa-r2-perl_2.086000~dfsg-8build5_amd64 
NAME
Marpa::R2::HTML - High-level HTML Parser
SYNOPSIS
Delete all tables:
use Marpa::R2::HTML qw(html);
my $with_table = 'Text<table><tr><td>I am a cell</table> More Text';
my $no_table = html( \$with_table, { table => sub { return q{} } });
Delete everything but tables:
my %handlers_to_keep_only_tables = (
table => sub { return Marpa::R2::HTML::original() },
':TOP' => sub { return \( join q{}, @{ Marpa::R2::HTML::values() } ) }
);
my $only_table = html( \$with_table, \%handlers_to_keep_only_tables );
The above works by turning the original text of the HTML into values and concatenating the values at the
top of the parse. The same logic works even if a table is very defective:
my $with_bad_table = 'Text<tr>I am a cell</table> More Text';
my $only_bad_table =
html( \$with_bad_table, \%handlers_to_keep_only_tables );
Delete all comments:
my $with_comment = 'Text <!-- I am a comment --> I am not a comment';
my $no_comment = html( \$with_comment,
{ ':COMMENT' => sub { return q{} } });
By default, text is passed through unchanged, so that the user need only specify semantic actions for
those components she wants changed. To change the title of a document:
my $old_title = '<title>Old Title</title>A little html text';
my $new_title = html(
\$old_title,
{ 'title' => sub { return '<title>New Title</title>' }
}
);
Delete all elements with a class attribute of ""delete_me"":
my $stuff_to_be_edited = '<p>A<p class="delete_me">B<p>C';
my $edited_stuff = html( \$stuff_to_be_edited,
{ '.delete_me' => sub { return q{} } });
Marpa::R2::HTML recognizes elements even if they have missing start and/or end tags. Marpa::R2::HTML can
supply missing tags:
sub supply_missing_tags {
my $tagname = Marpa::R2::HTML::tagname();
return if Marpa::R2::HTML::is_empty_element($tagname);
return ( Marpa::R2::HTML::start_tag() // "<$tagname>\n" )
. Marpa::R2::HTML::contents() .
( Marpa::R2::HTML::end_tag() // "</$tagname>\n" );
}
my $html_with_just_a_title = '<title>I am a title and That is IT!';
my $valid_html_with_all_tags =
html( \$html_with_just_a_title, { q{*} => \&supply_missing_tags } );
Marpa::R2::HTML understands the hierarchical structure of an HTML document. Finding the maximum nesting
depth in elements is straightforward:
sub depth_below_me {
return List::Util::max( 0, @{ Marpa::R2::HTML::values() } );
}
my %handlers_to_calculate_maximum_element_depth = (
q{*} => sub { return 1 + depth_below_me() },
':TOP' => sub { return depth_below_me() },
);
my $maximum_depth_with_just_a_title = html( \$html_with_just_a_title,
\%handlers_to_calculate_maximum_element_depth );
Marpa::R2::HTML tracks actual elements, however tagged. The above code returns the same depth for
$valid_html_with_all_tags as for $html_with_just_a_title.
DESCRIPTION
Marpa::R2::HTML does "high-level" parsing of HTML. It allows handlers to be specified for elements,
terminals and other components in the hierarchical structure of an HTML document. Marpa::R2::HTML is an
extremely liberal HTML parser. Marpa::R2::HTML does not reject any documents, no mater how poorly they
fit the HTML standards.
THE Marpa::R2::HTML::html STATIC METHOD
The interface to Marpa::R2::HTML is through the "Marpa::R2::HTML::html" static method. It is the only
Marpa::R2::HTML method not part of the API for the semantic actions.
"html" takes one or more arguments. The first argument is required, and must be a reference to a string
to be parsed as HTML. The second and subsequent arguments (all optional) are hash references with
handler descriptions. (See the synopsis for several examples of calls using the "html" method.)
CSS-style Handler Options
Handler descriptions in Marpa::R2::HTML are key-value pairs in a hash. In each pair, the key is a CSS-
style handler specifier, and the value is a closure, which is called the action for the handler.
Specifiers are "CSS-style" -- their syntax imitates some of the basic cases of CSS specifiers. No
attempt is planned to implement the full CSS specifier syntax.
Supported specifier syntaxes are as follows:
Tagname Specifiers
table => sub { return Marpa::R2::HTML::original() },
If a specifier contains no special characters it is taken as the name of an element. (A "special"
character is anything except an alphanumeric, a hyphen or an underscore.) Consistent with
HTML::Parser's default behavior, element names must be specified in lowercase.
Class Specifiers
A specifier which is a dot or period followed by a name will match any element whose class attribute
is the same as the specified name. For example, the specifier "".delete_me"" will match any element
whose class attribute is ""delete_me"".
Tagname-Class Pair Specifiers
A specifier which contains a dot or period somewhere other than the first position (such as
""span.label"") is treated as a dotted tagname-class pair. Its action will be called for any
component whose tagname and class attribute both match the specifiers.
The Tagname Wildcard Specifier
A specifier of just an asterisk (""*"") matches all elements. Be careful to note that matching all
elements is not the same as matching all components. The element wildcard specifier will not match
any pseudoclasses.
Pseudoclass Specifiers
':COMMENT' => sub { return q{} }
A specifier which begins with a colon ("":"") matches a pseudoclass. Marpa::R2::HTML defines
pseudoclasses to deal with terminals and other non-element components of the HTML hierarchy.
Conflicting Specifiers
At most one semantic action is called for each component. Where an element component matches several
specifiers, the action is picked based on the most specific match.
1. Matches by tagname-class pair are the most specific.
2. Matches by class are the next most specific.
3. Matches by tagname are considered less specific than matches by class.
4. The wildcard match is the least specific.
Here's an example:
my $html = <<'END_OF_HTML';
<span class="high">High Span</span>
<span class="low">Low Span</span>
<div class="high">High Div</div>
<div class="low">Low Div</div>
<div class="oddball">Oddball Div</div>
END_OF_HTML
our @RESULTS = ();
Marpa::R2::HTML::html(
\$html,
{ q{*} => sub {
push @RESULTS, 'wildcard handler: ' . Marpa::R2::HTML::contents();
},
'div' => sub {
push @RESULTS, '"div" handler: ' . Marpa::R2::HTML::contents();
},
'.high' => sub {
push @RESULTS, '".high" handler: ' . Marpa::R2::HTML::contents();
},
'div.high' => sub {
push @RESULTS,
'"div.high" handler: ' . Marpa::R2::HTML::contents();
},
'.oddball' => sub {
push @RESULTS,
'".oddball" handler: ' . Marpa::R2::HTML::contents();
},
'body' => sub {undef},
'head' => sub {undef},
'html' => sub {undef},
'p' => sub {undef},
}
);
Here is what $result would contain after the above code was run:
".high" handler: High Span
wildcard handler: Low Span
"div.high" handler: High Div
"div" handler: Low Div
".oddball" handler: Oddball Div
Details of the Specifier Syntax
For elements and class names only alphanumerics, hyphens and underscores are supported. Elements must be
specified in lowercase, but they will match tagnames in the original document on a case-insensitive
basis.
Forcing element names to be lowercase follows the default behavior of HTML::Parser, which coerces all
tagnames to lowercase. This is consistent with the HTML standards. It is not consistent with the XML
standards, and an option to configure this behavior may be added in the future.
Pseudoclass names special to Marpa::R2::HTML are case-sensitive, and must be all uppercase. Lowercase is
reserved for CSS pseudoclasses. The CSS standard specifies that its pseudoclass names are case-
indifferent. No CSS pseudoclasses are supported at this writing.
PSEUDOCLASSES
Marpa::R2::HTML uses HTML::Parser to do its low-level parsing. HTML::Parser "events" become the
terminals for Marpa::R2::HTML.
Besides terminals and elements, three other HTML components are recognized: the SGML prolog (":PROLOG"),
the SGML trailer (":TRAILER"), and the HTML document as a whole (":TOP").
:CDATA
The ":CDATA" pseudoclass specifies the action for CDATA terminals. Its action is called once for each
non-whitespace raw "text" event that is not reclassed as cruft. (Raw text is text in which any markup
and entities should be left as is.)
More precisely, a ":CDATA" terminal is created from any HTML::Parser "text" event that has the "is_cdata"
flag on; that contains a non-whitespace character as defined in the HTML 4.01 specification
(<http://www.w3.org/TR/html4/struct/text.html#h-9.1>); and that is not reclassed as cruft.
:COMMENT
The ":COMMENT" pseudoclass specifies the action for HTML comments. Its action is called once for every
"HTML::Parser" "comment" event that is not reclassed as cruft.
:CRUFT
The ":CRUFT" pseudoclass specifies the action for cruft. Its action is called once for every
"HTML::Parser" event that Marpa::R2::HTML reclasses as cruft.
Marpa::R2::HTML reclasses terminals as cruft when they do not fit the structure of an HTML document. One
example of a terminal that Marpa::R2::HTML would reclass as cruft is a "</head>" end tag in the HTML
body.
Reclassing terminals as cruft is only done as the last resort. When it can, HTML::Parser forgives
violations of the HTML standards and accepts terminals as non-cruft.
Cruft is treated in much the same way as comments. It is preserved, untouched, in the original text
view.
:DECL
The ":DECL" pseudoclass specifies the action for SGML declarations. Its action is called once for every
"HTML::Parser" "declaration" event that is not reclassed as cruft.
:PCDATA
The ":PCDATA" pseudoclass specifies the action for PCDATA terminals. Its action is called once for each
non-whitespace non-raw "text" event that is not reclassed as cruft.
More precisely, a ":PCDATA" terminal is created from any HTML::Parser "text" event that has the
"is_cdata" flag off; that contains a non-whitespace character as defined in the HTML 4.01 specification
(<http://www.w3.org/TR/html4/struct/text.html#h-9.1>); and that is not reclassed as cruft.
Markup and entities in ":PCDATA" text are expected to be interpreted eventually, but it can be counter-
productive to do this during parsing. An application may, for example, be rewriting a document for
display on the web. In that case it will often want to leave markup and entities for the client's
browser to interpret.
Marpa::R2::HTML leaves interpretation of markup and entities entirely to the application. An application
which chooses to do the interpretation itself may do it in the actions, or deal with it in post-
processing. CPAN has excellent tools for this, some of which are part of HTML::Parser.
:PI
The ":PI" pseudoclass specifies the action for SGML processing instructions. Its action is called once
for every HTML::Parser "process" event that is not reclassed as cruft.
:PROLOG
The ":PROLOG" pseudoclass specifies the action for SGML prolog. This is the part of the HTML document
which precedes the HTML root element. Components valid in the prolog include SGML comments, processing
instructions and whitespace.
:TOP
The action specified for the ":TOP" pseudoclass will be called once and only once in every parse, and
will be the last action called in every parse. The ":TOP" component is the entire physical document,
including the SGML prolog, the root element, and the SGML trailer. All the other HTML components in a
document will be descendants of the ":TOP" component.
The ":TOP" action is unique, in that there is always an action for it, even if one is not specified. The
"html" method returns the value returned by the ":TOP" action. The default ":TOP" action returns a
reference to a string with the literal text value of all of its descendants.
:TRAILER
The ":TRAILER" pseudoclass specifies the action for SGML trailer. This is the part of the HTML document
which follows the HTML root element. Components valid in the trailer include SGML comments, processing
instructions, and whitespace. Cruft can also be found here, though for Marpa::R2::HTML that is a last
resort.
:WHITESPACE
A Marpa::R2::HTML ":WHITESPACE" terminal is created for every HTML::Parser "text" event that is entirely
whitespace as defined in the HTML 4.01 specification
(<http://www.w3.org/TR/html4/struct/text.html#h-9.1>) and that is not reclassed as cruft. Whitespace is
acceptable in places where non-whitespace is not, and the difference can be very significant
structurally.
VIEWS
I hope the synopsis convinces the reader that the action semantics of Marpa::R2::HTML are natural. This
naturalness is achieved at the price of some novelty. This section explains the ideas behind the
semantic action API. Depending on taste, readers may want to skip this section and go straight to the
API.
The components of an HTML document form a hierarchy, with the ":TOP" component on top, and the terminals
on the bottom. The traditional syntax tree method requires semantic actions to know precisely what
children every component will have. This processing model is not a good fit to HTML. Marpa::R2::HTML
gives the writer of semantic actions "views" of each component that better fit situations where the
number and type of children is unknown or vaguely defined.
Marpa::R2::HTML's semantics focus more widely -- on a component's descendants instead of just its direct
children. (The terms ancestor and descendant are used in the standard way: If a component X is above Y
in the hierarchy, X is an ancestor of Y; and Y is a descendant of the X.)
The Original View
The original view sees the text of a component as it was originally passed to the parser. The original
view never changes. The original view is seen through the "Marpa::R2::HTML::original" API method.
The Terminals View
The terminals view sees the terminals corresponding to the original text of a component. The terminals
view never changes. The terminals view is usually seen as part of other views.
At this writing the API does not contain a "pure" terminals view method. For a terminals view of the
whole HTML document, HTML::Parser does the job with significantly lower overhead. For views and sections
of views with no values defined, the descendants view (described below) is equivalent to the terminals
view.
The Values View
When actions are called, they return a value. If that value is defined, it becomes visible to the values
view of its ancestors. The values view of a component sees the visible values for its descendants.
The values view is an array, with the values ordered according to the lexical order of the components
whose actions returned them. If no descendants have visible values, then the values view is a zero-
length array.
The values view is hierarchical. When a component produces a visible value, it makes the values of its
descendants disappear. That is, whenever the semantic action for a component X returns anything other
than a Perl "undef", it has two effects:
• That return value becomes the visible value associated with component X.
• All the values previously visible due to semantic actions for the descendants of component X
disappear.
Values which disappear are gone forever. There is no mechanism to make them "reappear".
As a special case, if an action for a component returns a Perl "undef", not only do the values of all its
descendants disappear, the component for the action also will not appear in the values view. When its
semantic action returns "undef", a component permanently "drops out" of the values view taking all
descendants with it. The original view is seen through the "Marpa::R2::HTML::values" API method.
The Literal View
The literal view can be thought of as a mix between the original view and the values view. It sees a
text string, like the original view. But unlike the original view, the literal view includes the visible
values.
Values appear in the literal view in stringized form. For sections of the original text without visible
values, the literal view is the same as the original view. In all Marpa::R2::HTML's views, whether
descendants are seen as text or values, they are seen in the original lexical order. The literal view is
seen through the "Marpa::R2::HTML::literal" API method.
The Descendants View
Just as the literal view can be thought of as a mix between the original view and the values view, the
descendants view can be thought of a mix between the terminals view and the values view.
The descendants view sees an array of elements with data for each of the component's descendants, in
lexical order. Where a value is visible, the descendants view sees data for the component with the
visible value. Where no value is visible, the descendants view sees data for the terminals. This means
that when no values are visible, the descendants view is the same as the terminals view.
The descendants view is implemented via the "Marpa::R2::HTML::descendants" method. It is the most fine-
grained and detailed way to look at the descendants of a component. The descendants view can do anything
that the other views can do, but the other views should be preferred when they fit the application.
Other views are typically more intuitive and efficient.
Views versus Syntax Trees
Views are a generalization of the traditional method for processing semantics: syntax trees. The values
view is the view that most closely resembles a syntax tree. But there are important differences.
In its purest form, the syntax tree model required the semantic actions to define exactly how many and
what kind of immediate children each node had. Each node in a syntax tree worked with its immediate
children. Children in a syntax tree appeared as values.
The values view, on the other hand, sees all its descendants, not just its immediate children, but only
if they make themselves visible. Because of this, the values view lends itself to being mixed with other
views. The values view allows pieces of the tree to decide when they will come into sight and when they
will fall out of view.
Views and Efficiency
In most applications, views are more efficient than syntax trees. In terms of Marpa::R2::HTML views,
traditional syntax tree processing corresponds most closely to the values view when every component in
the parse has a visible value. For Marpa::R2::HTML this is close to the worst case.
Marpa::R2::HTML optimizes for unvalued components. Unvalued components are represented as terminal
spans. Adjacent descendant spans are automatically merged. This means the size and time required do not
increase as processing rises up the component hierarchy.
Terminals views are calculated on a just-in-time basis when they are requested through the action API.
The terminals view is produced quickly from the merged terminal span.
Original views are also calculated on a just-in-time basis as requested. Each terminal tracks the text
it represents as a character span. The original text can be quickly reconstructed as the text in the
source document from the first character location of its component's first terminal to the last character
location of the component's last terminal.
When a handler does not need to return a value, the most efficient thing to do is to return "undef".
This reverts that component and all its descendants to the efficient unvalued representation.
THE SEMANTIC ACTION API
Marpa::R2::HTML's semantic action API is implemented mainly through context-aware static methods. No
arguments are passed to the user's semantics action callbacks. Instead the semantic actions get whatever
data they need by calling these static methods.
API Static Methods
Marpa::R2::HTML::attributes
Returns a hash ref to the attributes of the start tag. This hash ref is exactly the hash ref
returned for the "attr" arg specification of HTML::Parser. The "attributes" API method returns an
empty hash if there were no attributes, if there was no start tag for this element, or if the current
component is not an element.
Marpa::R2::HTML::contents
For an element, returns the literal view of the contents. The contents of an element are its entire
text except for its start tag and its end tag. For an non-element component, returns undef.
Marpa::R2::HTML::descendants
This static method implements the descendants view. It takes one argument, the "dataspec". The
dataspec is a string specifying the data to be returned for each descendant. The "descendants"
method returns a reference to an array with one element per descendant, in lexical order. Each
element in the array is a reference to an array whose elements are the per-descendant data requested
in the string.
The descendant data specification string has a syntax similar to that of the "argspec" strings of
HTML::Parser. Details of that syntax are given below
Marpa::R2::HTML::end_tag
For an element with an explicit end tag, returns the original text of the end tag. For non-element
components, returns undef. For elements with no end tag, returns undef.
Marpa::R2::HTML::is_empty_element
For an element, returns a Perl true value if the element is empty, a defined Perl false value
otherwise. For non-element components, returns undef.
Marpa::R2::HTML::literal
The "Marpa::R2::HTML::literal" method implements the literal view. Returns a string containing the
literal view of the component -- its text as modified by any the visible values of its descendants.
Marpa::R2::HTML::literal_ref
Returns a reference to a string containing the literal view of the component. This can be useful for
very long strings.
Marpa::R2::HTML::offset
Returns the start offset of the component. This is a zero-based location in the source document.
Some components are zero-length, containing none of the tokens in the physical input. The
"Marpa::R2::HTML::offset" method return "undef" for these.
Marpa::R2::HTML::original
The "Marpa::R2::HTML::original" method implements the original view. Returns a string containing the
original view of the component -- its text unchanged from the source document.
Marpa::R2::HTML::start_tag
For an element with an explicit start tag, returns the original text of the start tag. For non-
element components, returns undef. For elements with no explicit start tag, returns undef.
Marpa::R2::HTML::tagname
For an element component, returns its tagname. There is a tagname even if there are no explicit
tags. Tagname is determined based on structure. For non-element components, returns undef.
Marpa::R2::HTML::title
Returns the value of the title attribute. For a non-element component, returns undef. If there was
no explicit start tag, returns undef. If there was no title attribute, returns undef.
Marpa::R2::HTML::token_type
For a token, returns the token type. The token types are the event types from HTML::Parser: ""T""
for text, ""S"" for a start tag, ""E"" for an end tag, ""PI"" for a processing instruction, ""D"" for
an SGML declaration, and ""C"" for a comment. If the component is an element or some other non-
token, returns undef.
Marpa::R2::HTML::values
The "Marpa::R2::HTML::values" method implements the values view. It returns a reference to an array
of the descendant values visible from this component, in lexical order. No elements of this array
will be undefined. The array will be zero length if no descendant has a visible value.
Dataspecs
Marpa::R2::HTML::descendants('token_type,literal,element')
The data specification string, or dataspec, is a comma separated list of descendant data specifiers. The
"Marpa::R2::HTML::descendants" method takes a dataspec as its argument. The
"Marpa::R2::HTML::descendants" method returns a reference to an array of references to arrays of per-
descendant data. The contents of the per-descendant data arrays and their order is as specified by the
dataspec. These are the valid descendant data specifiers:
"element"
For an element descendant, returns the tagname. A valid tagname is returned even if there were no
explicit tags. For non-element descendants, returns undef.
"literal"
Returns a string containing the literal view of the descendant.
"original"
Returns a string containing the original view of the descendant.
"token_type"
If the descendant is a terminal, returns the token type. Token types are as described for the
"Marpa::R2::HTML::token_type" API method. For components with visible values, returns undef.
"value"
For element descendants with a value, returns that value. In all other cases, returns undef.
The Instance Hash
Each Marpa::R2::HTML instance makes available a per-instance variable as a scratchpad for the
application: $Marpa::R2::HTML::INSTANCE. Each call to Marpa::R2::HTML::html creates a
$Marpa::R2::HTML::INSTANCE variable which is reserved for that application using the "local" keyword.
Marpa::R2::HTML::html initializes it to an empty hash, but after that does not touch it. When
programming via side effects is more natural than passing data up the parse tree (and it often is),
$Marpa::R2::HTML::INSTANCE can be used to store the data.
Ordinarily, $Marpa::R2::HTML::INSTANCE is destroyed, with the rest of the parse instance, when
"Marpa::R2::HTML::html" returns. But it can be useful for the ":TOP" semantic action to return
$Marpa::R2::HTML::INSTANCE as the value of the parse.
Undefined Actions versus Actions Which Return "undef"
It is worth emphasizing that the effect of not defining a semantic action for a component is different
from the effect of defining a semantic action which returns a Perl "undef". The difference lies in what
happens to any visible values of the descendants of that component.
Where no action is defined for a component, it leaves all that component's views as they were before.
That is, all values which were visible remain visible and no new values become visible. When an action
is defined for a component, but that action returns undef, no new values become visible, and all
descendant values which were visible disappear.
Root Element versus :TOP Pseudoclass
It is important to understand the very special function of the ":TOP" component, and to avoid confusing
it with the HTML root element. The most important distinctions are that
• The semantic action for ":TOP" pseudoclass is always the last action to be called in a parse.
• The ":TOP" component is always the entire HTML document. This can be true of the root element, but
it is not true in all cases.
• The value that the action for the ":TOP" component returns becomes the value that the
Marpa::R2::HTML::html method returns.
The root element is the HTML element whose tagname is ""html"", though its start and end tags are
optional and can be omitted even in strictly valid HTML. Tags or no tags, every HTML document has a root
element. (The ":TOP" component is not an element, so it does not have a tagname and never has tags.)
The root element is always a descendant of the ":TOP" component. The SGML prolog and SGML trailer are
always descendants of the ":TOP" component. The SGML prolog and SGML trailer are never descendants of
the root element.
If an action for the root element is specified, it will also be called once and only once in every parse.
An action for the root element can be specified in same way as actions for other elements, using its
tagname of ""html"". An element wildcard action also becomes the action for the root element, if no more
specific handler declaration takes precedence.
A ":TOP" action will be called once and only once in every parse. The ":TOP" action is unique in that
there is a default action. No other component has a default action.
Tags versus Structure
Where tags conflict with structure, HTML::Parser follows structure. "Following structure" means that,
for example, if semantic actions for the "html", "head", and "body" elements exist, they will be called
once and only once during every parse.
Consider this short and very defective HTML document:
<title>Short</title><p>Text</head><head>
HTML::Parser starts the HTML document's body when it encounters the "<p>" start tag. That means that,
even if they were in the right order, the two "head" tags cannot be fit into any reasonable parse
structure.
If an action is specified for the "head" element, it will be called for the actual header, and the
original view of the "head" element component will be the text ""<title>Short</title>"". The action for
the "head" element will not be called again. The two stray tags, "</head>" and "<head>", will be treated
as descendants of the "body" element, and reclassed as "cruft" terminals.
Explicit and Implicit Elements
If a semantic action is specified for a tagname, it is called whenever an element is found with that
tagname, even if there are no explicit tags for that element. The HTML standards allow both start and
end tags to be missing for "html", "head", "body" and "tbody" elements. Marpa::R2::HTML is more liberal,
and will recognize virtual tags for "table", "tr", and "td" elements as required to repair a defective
table.
Marpa::R2::HTML is more even liberal about recognizing virtual end tags than it is about start tags.
Virtual start tags are recognized only for the specific elements listed above. For any non-empty HTML
element, there is some circumstance under which Marpa::R2::HTML will recognize a virtual end tag. At end
of file, as one example, Marpa::R2::HTML will do its best to produce a balanced HTML structure by
creating a virtual end tag for every element in the stack of currently active elements.
EXPORTS
Marpa::R2::HTML exports nothing by default. Optionally, Marpa::R2::HTML::html may be exported.
Copyright and License
Copyright 2014 Jeffrey Kegler
This file is part of Marpa::R2. Marpa::R2 is free software: you can
redistribute it and/or modify it under the terms of the GNU Lesser
General Public License as published by the Free Software Foundation,
either version 3 of the License, or (at your option) any later version.
Marpa::R2 is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser
General Public License along with Marpa::R2. If not, see
http://www.gnu.org/licenses/.