NAME
MarpaX::xPathLike - a xPath like processor for perl data-structures
(hashes and arrays)!
VERSION
Version 0.2
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:
* RT: CPAN's request tracker (report bugs here)
http://rt.cpan.org/NoAuth/Bugs.html?Dist=MarpaX-xPathLike
* AnnoCPAN: Annotated CPAN documentation
http://annocpan.org/dist/MarpaX-xPathLike
* CPAN Ratings
http://cpanratings.perl.org/d/MarpaX-xPathLike
* Search CPAN
http://search.cpan.org/dist/MarpaX-xPathLike/
ACKNOWLEDGEMENTS
I would like to say thansk to amon / Lukas Atkinson for scrutinized the
code i 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
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otherwise transfer the Package with respect to any patent claims
licensable by the Copyright Holder that are necessarily infringed by the
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