MarpaX::xPathLike - a xPath like processor for perl data-structures (hashes and arrays)!
Version 0.203
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)]
$)->getvalues();
The xPathLike uses the xPath 1.0 syntax to query any set of complex perl data structures, using keys or indexes for defining the path. Examples:
/0/invoice/Total
/2
/*/invoice[Total>100]/Total
//Tax
//Total[../Tax = .2]
//*[count(itens/*) > 1][1]
sum(//Total)
Like as in xPath it's also possible to query a function.
How to use it.
use strict;
use MarpaX::xPathLike;
use Data::Dumper;
($\,$,) = ("\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.
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()]
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.
Used only internally!!! Do nothing;
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.
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.
Executes the query over data and returns a MarpaX::xPathLike::Results object
Compile a xPathLike string, query the data and returns a MarpaX::xPathLike::Results object
Returns a list os references for each matched data;
Returns a reference for first matched data;
Returns a list of values for each matched data;
Returns the value of first matched data;
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.
- self::
- child::
- parent::
- ancestor::
- ancestor-or-self::
- descendant::
- descendant-or-self::
- preceding-sibling::
- following::sibling::
- 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).
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
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/{'"'}
Isidro Vila Verde, <jvverde at gmail.com>
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.
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)
-
AnnoCPAN: Annotated CPAN documentation
-
CPAN Ratings
-
Search CPAN
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.
Copyright 2013 Isidro Vila Verde.
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