Crystal XPath2
Crystal XPath2 Shard provide XPath implementation in Pure Crystal. Performs the compilation of XPath expression and provides mechanism to select/evaluate nodes from HTML or other documents using XPath expression
Supported Features
The basic XPath patterns.
The basic XPath patterns cover 90% of the cases that most stylesheets will need.
node
: Selects all child elements with node Name of node.
*
: Selects all child elements.
@attr
: Selects the attribute attr.
@*
: Selects all attributes.
node()
: Matches an org.w3c.dom.Node.
text()
: Matches a org.w3c.dom.Text node.
comment()
: Matches a comment.
.
: Selects the current node.
..
: Selects the parent of current node.
/
: Selects the document node.
a[expr]
: Select only those nodes matching a which also satisfy the expression expr.
a[n]
: Selects the nth matching node matching a When a filter's expression is a number, XPath selects based on position.
a/b
: For each node matching a, add the nodes matching b to the result.
a//b
: For each node matching a, add the descendant nodes matching b to the result.
//b
: Returns elements in the entire document matching b.
a|b
: All nodes matching a or b, union operation(not boolean or).
(a, b, c)
: Evaluates each of its operands and concatenates the resulting sequences, in order, into a single result sequence
Node Axes
child::*
: The child axis selects children of the current node.
descendant::*
: The descendant axis selects descendants of the current node. It is equivalent to"//"
.
descendant-or-self::*
: Selects descendants including the current node.
attribute::*
: Selects attributes of the current element. It is equivalent to@*
following-sibling::*
: Selects nodes after the current node.
preceding-sibling::*
: Selects nodes before the current node.
following::*
: Selects the first matching node following in document order, excluding descendants.
preceding::*
: Selects the first matching node preceding in document order, excluding ancestors.
parent::*
: Selects the parent if it matches. The".."
pattern from the core is equivalent to 'parent::node()'.
ancestor::*
: Selects matching ancestors.
ancestor-or-self::*
: Selects ancestors including the current node.
self::*
: Selects the current node.'.'
is equivalent to"self::node()"
.
Expressions
Shard supports three types: number, boolean, string.
path
: Selects nodes based on the path.
a = b
: Standard comparisons.
* a `=` b `true` if a equals b.
* a `!=` b `true` if a is not equal to b.
* a `<` b `true` if a is less than b.
* a `<=` b `true` if a is less than or equal to b.
* a `>` b `true` if a is greater than b.
* a `>=` b `true` if a is greater than or equal to b.
a + b
: Arithmetic expressions.
* `- a` Unary minus
* a `+` b Add
* a `-` b Substract
* a `*` b Multiply
* a `div` b Divide
* a `mod` b Floating point mod, like Java.
a or b
: Booleanor
operation.
a and b
: Booleanand
operation.
(expr)
: Parenthesized expressions.
fun(arg1, ..., argn)
: Function calls:
| Function | Supported |
| --- | --- |
boolean()
| ✓ |
ceiling()
| ✓ |
choose()
| ✗ |
concat()
| ✓ |
contains()
| ✓ |
count()
| ✓ |
current()
| ✗ |
document()
| ✗ |
element-available()
| ✗ |
ends-with()
| ✓ |
false()
| ✓ |
floor()
| ✓ |
format-number()
| ✗ |
function-available()
| ✗ |
generate-id()
| ✗ |
id()
| ✗ |
key()
| ✗ |
lang()
| ✗ |
last()
| ✓ |
local-name()
| ✓ |
name()
| ✓ |
namespace-uri()
| ✓ |
normalize-space()
| ✓ |
not()
| ✓ |
number()
| ✓ |
position()
| ✓ |
replace()
| ✓ |
reverse()
| ✓ |
round()
| ✓ |
starts-with()
| ✓ |
string()
| ✓ |
string-length()
| ✓ |
substring()
| ✓ |
substring-after()
| ✓ |
substring-before()
| ✓ |
sum()
| ✓ |
system-property()
| ✗ |
translate()
| ✓ |
true()
| ✓ |
unparsed-entity-url()
| ✗ |
Installation
- Add the dependency to your
shard.yml
:
`yaml
dependencies:
xpath2:
github: naqvis/crystal-xpath2
`
- Run
shards install
Usage
refer to spec
for usage examples or refer to Crystal HTML5 and JSON XPath for implementation details.
Development
To run all tests:
crystal spec
Contributing
- Fork it (<https://github.com/naqvis/crystal-xpath2/fork>)
- Create your feature branch (
git checkout -b my-new-feature
) - Commit your changes (
git commit -am 'Add some feature'
) - Push to the branch (
git push origin my-new-feature
) - Create a new Pull Request
Contributors
- Ali Naqvi - creator and maintainer