/**
* Creates a new collection of rules.
*
* You must provide a list of rules, the following formats are accepted:
*
* #### Rules as arrays
*
* ``php
* [
* 'S -> a A' => function (&$info) { },
* 'A -> b B' => function (&$info) { },
* 'B -> c', // semantic routine is optional
* ....
* ]
* ```
*
* #### Rules as a single string
*
* In this case no semantic routine is given for each rule
*
* ```php
* [
* 'S -> a A',
* 'A -> b B',
* 'C -> c',
* ]
* ```
*
* #### Rules as a rule objects
*
* ```php
* [
* new Rule('S -> a A', function (&$info) { }),
* new Rule('A -> b B', function (&$info) { }),
* new Rule('B -> c'), // semantic routine is optional
* ]
* ```
*
* ---
*
* Of course you can combine formats:
*
* ```php
* [
* 'S -> a A' => function($info) { },
* 'A -> b B',
* new Rule('B -> c'),
* ]
* ```
*
* @param array $collection List of rules given as an array
* @return void
*/
public function __construct(array $collection = [])
{
if (empty($collection)) {
return;
}
$i = 0;
foreach ($collection as $index => $rule) {
if (!$rule instanceof Rule) {
if (is_string($index) && is_callable($rule)) {
// 'S -> a' => function()
$left = $index;
$right = $rule;
} elseif (is_integer($index) && is_string($rule)) {
// 0 => 'S -> a'
$left = $rule;
$right = '';
}
if (isset($left) && isset($right)) {
$rule = new Rule($left, $right);
unset($left, $right);
}
}
if (!$rule instanceof Rule) {
continue;
}
array_unshift($this->_variables, $rule->lhs());
if ($i == 0) {
$this->_startVariable = $rule->lhs();
}
$this->_rules[] = $rule;
$i++;
}
$this->_variables = array_unique($this->_variables);
foreach ($this->_rules as $rule) {
$rhs = $rule->rhs();
$rhs = explode(' ', $rhs);
$rhs = array_diff($rhs, $this->_variables);
$this->_terminals = array_merge($this->_terminals, $rhs);
}
$this->_terminals = array_unique($this->_terminals);
}
