++ed by:
PWBENNETT ZMUGHAL

2 PAUSE users

Isidro Vila Verde

NAME

MarpaX::xPathLike - a xPath like processor for perl data-structures (hashes and arrays)!

VERSION

Version 0.203

Why we need another one

There are already some good approaches to xPath syntax, namely the Data::dPath and Data::Path. Nevertheless we still missing some of powerfull constructions as provided by xPath. Suppose, for example, we have an array of invoices with Total, Amount and Tax and need to check which one does not comply to the rule "Total = Amount * (1+Tax)".

For the data structure below we can easily achieve it with this code:

     use MarpaX::xPathLike;
     use Data::Dumper;

     ($\,$,) = (qq|\n|, q|,|);
     my $data = MarpaX::xPathLike->data([
             {invoice => {
                             Amount => 100,
                             Tax => 0.2,
                             Total => 120
                     }
             },
             {invoice => {
                             Amount => 200,
                             Tax => 0.15,
                             Total => 240
                     }       
             },
             receipt =>{ 
             }
     ]);

     print Dumper $data->query(q$
             //invoice[Total != Amount * (1 + Tax)]
     $)->getvalues();

The xPathLike uses the xPath 1.0 syntax to query any set of complex perl data structures, using keys or indexes for defining the path. Examples:

     /0/invoice/Total
     /2
     /*/invoice[Total>100]/Total
     //Tax
     //Total[../Tax = .2]
     //*[count(itens/*) > 1][1]
     sum(//Total)

Like as in xPath it's also possible to query a function.

SYNOPSIS

How to use it.

     use strict;
     use MarpaX::xPathLike;
     use Data::Dumper;

     ($\,$,) = ("\n",",");
     my $d = {
          drinks => {
               q|Alcoholic beverage| => 'not allowed',
               q|Soft drinks| => [qw|Soda Coke|]
          },
          food => { 
               fruit => [qw|bananas apples oranges pears|], 
               vegetables  => [qw|potatoes  carrots tomatoes|]
          } 
     };

     my $data = MarpaX::xPathLike->data($d);
     my $results = $data->query(q|/*/*/0|);
     my @values = $results->getvalues();
     print @values;                         
     #Soda,bananas,potatoes

     my $ref = $results->getref();
     $$ref = 'Tonic';
     print $d->{drinks}->{q|Soft drinks|}->[0];     
     #Tonic

To get values we can invoke the getvalues ou getvalue methods to obtain a list/element matched. If what we need is to change the values we can use getrefs or getref methods to obtain a reference to the matched data-structures. The getref(s) methods always returns a reference to matched data-structure. If the matched element is a scalar a reference to that scalar is returned. If the matched element is a reference array (or hash) a reference to that reference is returned, so we can change it and not only nested data-structures.

DESCRIPTION

It looks for complex perl data-structures which match the xPathLike expression and returns a list of matched data-structures.

Like xPath it is possible to deal with any logical or arithmetic expressions, ex:

    *{count(a) == count(c) / 2 * (1 + count(b)) or d}

, or even query xPath functions ex:

    count(//*)
    name(//*[last()])
    sum(//[*])

Additionally some extensions are implemented to deal with perl data-structures, namely to choose between arrays and hashes.

Example:

Get all structures but only one which are arrays

     //[*]

Similarly to get all of hash structures, we can write

     //{*}

Besides that, some extra functions are also provide to check data type in predicates, ex:

     //*[isScalar()]

METHODS

The MarpaX::xPathLike just provides two useful methods, compile and data. The first is used to compile a xPathLike expression and the second is used to prepare data to be queried.

MarpaX::xPathLike methods

new()

Used only internally!!! Do nothing;

compile(xPathLikeString)

     my $query = MarpaX::xPathLike->compile('*');                #compile the query
     
     my @values1 = $query->data({fruit => 'bananas'})->getvalues();
     # @values1 = (bananas)

     my @values2 = $query->data({
          fruit => 'bananas', 
          vegetables => 'orions'
     })->getvalues();
     # @values2 = (bananas, orions)

     my @values3 = $query->data({
          food => {fruit => 'bananas'}
     })->getvalues();
     # @values3 = ({fruit => 'bananas'})

The compile method receives a xPathLike string, compiles it and returns a MarpaX::xPathLike::Data object. This is the prefered method to run the same query over several data-structures.

data(dataRef)

    my $data = MarpaX::xPathLike->data({
           food => {
                   fruit => 'bananas',
                   vegetables => 'unions'
           },
           drinks => {
                   wine => 'Porto',
                   water => 'Evian'
           }
    });


    my @values1 = $data->query('/*/*')->getvalues();
    print @values1; # Evian,Porto,bananas,unions

    my @values2 = $data->query('/*/wine')->getvalues();
    print @values2; #Porto

    #using a predicate, to get only first level entry which contains a fruit key
    my @values3 = $data->query('/*[fruit]/*')->getvalues();
    print @values3; #bananas,unions
    #using another filter to return only elements which have the value matching 
    #a /an/ pattern
    my @values4 = $data->query('/*/*[. ~ "an"]')->getvalues();
    print @values4;# Evian,bananas

    my @values5 = $data->query('//*[isScalar()]')->getvalues();
    print @values5;#Evian,Porto,bananas,unions

                  

The method data receives a hash (or array) reference and returns a MarpaX::xPathLike::Compile object. This is the prefered method to run several query over same data.

MarpaX::xPathLike::Data methods

data(data)

Executes the query over data and returns a MarpaX::xPathLike::Results object

MarpaX::xPathLike::Compiler methods

query(xPathLikeString)

Compile a xPathLike string, query the data and returns a MarpaX::xPathLike::Results object

MarpaX::xPathLike::Results methods

getrefs()

Returns a list os references for each matched data;

getref()

Returns a reference for first matched data;

getvalues()

Returns a list of values for each matched data;

getvalue()

Returns the value of first matched data;

xPath Compability

Unless some xPath functions, not yet implemented, and xPath axis preceding:: and following:: directions everything else is implemented. Probably buggly, sorry. I hope to fixe them as soon someone (?) identify them.

Supported axis

self::
child::
parent::
ancestor::
ancestor-or-self::
descendant::
descendant-or-self::
preceding-sibling::
following::sibling::

Supported Functions

count(path?)
sum(path)
name(path?)
position(path?)
last()
not(expr)
names(path?)*
values(path?)*
value(path?)*

(*) not a xPath 1.0 function.

names is like name but returns a list of names.

We don't support the text() funcions as we don't know what that should mean in perl data-structures context, but the value() and values() functions are provided to return the value/values of current context if path argument is missing or the value/values of matched data-structures. That/those value/values could be scalar(s) or hash/array reference(s).

Supported operators

The xPath supported operators are the following:

    +, -, *, div, %, =, !=, (), "", '', +, -, ., .., /, //, ::, <, <=, >, >=, [], and, or 
      and 
    | (paths union)

Addicionaly xPathLike also supports the following operators

    eq, ne, lt, le, gt, ge and ~ 

The ~ is the matching operator

Support for data types

In xPathLike path expression, a digit step could mean a array index or a hash's key name. ex:

    /a/0/b

may refere to a $d->{a}->[0]->{b} or to a $d->{a}->{0}->{b}. If a restriction is required for select only array's index 0 the xPathLike expression should be

    /a/[0]/b

And similarly for hash' key '0'

    /a/{0}/b

The curly bracket could also be useful to refere to keys with spaces or any special character with the help of quotes (singles or doubles). Some examples

    /{'five words as a keys'}//{"key with a / or a +"}/*

The curly and square brackets could also be used with axis and wildcard *. Examples:

    //{*}
    //[*]
    //*/parent::[b]
    //a//parent::{*}
    //*[self::{*} = 3 or self::[*] > 10]
    /1/[*][4]/child::[*][1]/{a}/following-sibling::*[last()]

If a hash key is just a * (or any other special character) the path expression could be something like this

    //{"*"}/b
    //a/{'*'}
    //{"+"}/b
    //a/{'/'}
    //{"}"}/b
    //a/{'"'}

AUTHOR

Isidro Vila Verde, <jvverde at gmail.com>

BUGS

Send email to <jvverde at gmail.com> with subject MarpaX::xPathLike or report any bugs or feature requests to bug-data-xPathLike at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=MarpaX-xPathLike. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc MarpaX::xPathLike

You can also look for information at:

ACKNOWLEDGEMENTS

I would like to say thanks to amon / Lukas Atkinson for scrutinized the code give me such valuable feedback. To Ron Savage for introduce me to the Marpa::R2 and all your help with UTF8 problems and good advices. To Jean-Damien to point me some importante issues on first release. And final a big Thank you to Jeffrey Kegler for creating the Marpa::R2.

LICENSE AND COPYRIGHT

Copyright 2013 Isidro Vila Verde.

This program is free software; you can redistribute it and/or modify it under the terms of the the Artistic License (2.0). You may obtain a copy of the full license at:

http://www.perlfoundation.org/artistic_license_2_0

Any use, modification, and distribution of the Standard or Modified Versions is governed by this Artistic License. By using, modifying or distributing the Package, you accept this license. Do not use, modify, or distribute the Package, if you do not accept this license.

If your Modified Version has been derived from a Modified Version made by someone other than you, you are nevertheless required to ensure that your Modified Version complies with the requirements of this license.

This license does not grant you the right to use any trademark, service mark, tradename, or logo of the Copyright Holder.

This license includes the non-exclusive, worldwide, free-of-charge patent license to make, have made, use, offer to sell, sell, import and otherwise transfer the Package with respect to any patent claims licensable by the Copyright Holder that are necessarily infringed by the Package. If you institute patent litigation (including a cross-claim or counterclaim) against any party alleging that the Package constitutes direct or contributory patent infringement, then this Artistic License to you shall terminate on the date that such litigation is filed.

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