351 lines
7.4 KiB
PHP
351 lines
7.4 KiB
PHP
<?php
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/**
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* A gettext Plural-Forms parser.
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*
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* @since 4.9.0
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*/
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if ( ! class_exists( 'Plural_Forms', false ) ) :
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class Plural_Forms {
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/**
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* Operator characters.
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*
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* @since 4.9.0
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* @var string OP_CHARS Operator characters.
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*/
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const OP_CHARS = '|&><!=%?:';
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/**
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* Valid number characters.
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*
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* @since 4.9.0
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* @var string NUM_CHARS Valid number characters.
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*/
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const NUM_CHARS = '0123456789';
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/**
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* Operator precedence.
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*
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* Operator precedence from highest to lowest. Higher numbers indicate
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* higher precedence, and are executed first.
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*
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* @see https://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B#Operator_precedence
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*
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* @since 4.9.0
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* @var array $op_precedence Operator precedence from highest to lowest.
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*/
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protected static $op_precedence = array(
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'%' => 6,
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'<' => 5,
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'<=' => 5,
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'>' => 5,
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'>=' => 5,
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'==' => 4,
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'!=' => 4,
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'&&' => 3,
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'||' => 2,
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'?:' => 1,
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'?' => 1,
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'(' => 0,
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')' => 0,
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);
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/**
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* Tokens generated from the string.
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*
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* @since 4.9.0
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* @var array $tokens List of tokens.
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*/
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protected $tokens = array();
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/**
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* Cache for repeated calls to the function.
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*
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* @since 4.9.0
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* @var array $cache Map of $n => $result
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*/
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protected $cache = array();
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/**
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* Constructor.
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*
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* @since 4.9.0
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*
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* @param string $str Plural function (just the bit after `plural=` from Plural-Forms)
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*/
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public function __construct( $str ) {
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$this->parse( $str );
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}
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/**
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* Parse a Plural-Forms string into tokens.
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*
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* Uses the shunting-yard algorithm to convert the string to Reverse Polish
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* Notation tokens.
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*
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* @since 4.9.0
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*
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* @throws Exception If there is a syntax or parsing error with the string.
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*
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* @param string $str String to parse.
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*/
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protected function parse( $str ) {
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$pos = 0;
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$len = strlen( $str );
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// Convert infix operators to postfix using the shunting-yard algorithm.
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$output = array();
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$stack = array();
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while ( $pos < $len ) {
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$next = substr( $str, $pos, 1 );
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switch ( $next ) {
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// Ignore whitespace.
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case ' ':
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case "\t":
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$pos++;
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break;
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// Variable (n).
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case 'n':
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$output[] = array( 'var' );
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$pos++;
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break;
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// Parentheses.
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case '(':
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$stack[] = $next;
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$pos++;
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break;
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case ')':
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$found = false;
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while ( ! empty( $stack ) ) {
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$o2 = $stack[ count( $stack ) - 1 ];
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if ( '(' !== $o2 ) {
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$output[] = array( 'op', array_pop( $stack ) );
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continue;
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}
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// Discard open paren.
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array_pop( $stack );
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$found = true;
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break;
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}
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if ( ! $found ) {
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throw new Exception( 'Mismatched parentheses' );
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}
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$pos++;
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break;
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// Operators.
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case '|':
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case '&':
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case '>':
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case '<':
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case '!':
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case '=':
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case '%':
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case '?':
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$end_operator = strspn( $str, self::OP_CHARS, $pos );
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$operator = substr( $str, $pos, $end_operator );
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if ( ! array_key_exists( $operator, self::$op_precedence ) ) {
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throw new Exception( sprintf( 'Unknown operator "%s"', $operator ) );
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}
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while ( ! empty( $stack ) ) {
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$o2 = $stack[ count( $stack ) - 1 ];
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// Ternary is right-associative in C.
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if ( '?:' === $operator || '?' === $operator ) {
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if ( self::$op_precedence[ $operator ] >= self::$op_precedence[ $o2 ] ) {
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break;
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}
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} elseif ( self::$op_precedence[ $operator ] > self::$op_precedence[ $o2 ] ) {
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break;
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}
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$output[] = array( 'op', array_pop( $stack ) );
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}
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$stack[] = $operator;
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$pos += $end_operator;
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break;
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// Ternary "else".
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case ':':
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$found = false;
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$s_pos = count( $stack ) - 1;
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while ( $s_pos >= 0 ) {
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$o2 = $stack[ $s_pos ];
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if ( '?' !== $o2 ) {
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$output[] = array( 'op', array_pop( $stack ) );
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$s_pos--;
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continue;
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}
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// Replace.
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$stack[ $s_pos ] = '?:';
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$found = true;
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break;
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}
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if ( ! $found ) {
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throw new Exception( 'Missing starting "?" ternary operator' );
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}
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$pos++;
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break;
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// Default - number or invalid.
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default:
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if ( $next >= '0' && $next <= '9' ) {
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$span = strspn( $str, self::NUM_CHARS, $pos );
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$output[] = array( 'value', intval( substr( $str, $pos, $span ) ) );
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$pos += $span;
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break;
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}
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throw new Exception( sprintf( 'Unknown symbol "%s"', $next ) );
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}
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}
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while ( ! empty( $stack ) ) {
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$o2 = array_pop( $stack );
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if ( '(' === $o2 || ')' === $o2 ) {
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throw new Exception( 'Mismatched parentheses' );
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}
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$output[] = array( 'op', $o2 );
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}
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$this->tokens = $output;
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}
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/**
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* Get the plural form for a number.
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*
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* Caches the value for repeated calls.
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*
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* @since 4.9.0
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*
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* @param int $num Number to get plural form for.
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* @return int Plural form value.
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*/
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public function get( $num ) {
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if ( isset( $this->cache[ $num ] ) ) {
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return $this->cache[ $num ];
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}
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$this->cache[ $num ] = $this->execute( $num );
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return $this->cache[ $num ];
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}
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/**
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* Execute the plural form function.
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*
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* @since 4.9.0
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*
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* @throws Exception If the plural form value cannot be calculated.
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*
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* @param int $n Variable "n" to substitute.
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* @return int Plural form value.
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*/
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public function execute( $n ) {
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$stack = array();
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$i = 0;
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$total = count( $this->tokens );
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while ( $i < $total ) {
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$next = $this->tokens[ $i ];
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$i++;
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if ( 'var' === $next[0] ) {
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$stack[] = $n;
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continue;
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} elseif ( 'value' === $next[0] ) {
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$stack[] = $next[1];
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continue;
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}
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// Only operators left.
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switch ( $next[1] ) {
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case '%':
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$v2 = array_pop( $stack );
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$v1 = array_pop( $stack );
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$stack[] = $v1 % $v2;
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break;
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case '||':
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$v2 = array_pop( $stack );
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$v1 = array_pop( $stack );
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$stack[] = $v1 || $v2;
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break;
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case '&&':
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$v2 = array_pop( $stack );
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$v1 = array_pop( $stack );
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$stack[] = $v1 && $v2;
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break;
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case '<':
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$v2 = array_pop( $stack );
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$v1 = array_pop( $stack );
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$stack[] = $v1 < $v2;
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break;
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case '<=':
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$v2 = array_pop( $stack );
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$v1 = array_pop( $stack );
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$stack[] = $v1 <= $v2;
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break;
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case '>':
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$v2 = array_pop( $stack );
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$v1 = array_pop( $stack );
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$stack[] = $v1 > $v2;
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break;
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case '>=':
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$v2 = array_pop( $stack );
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$v1 = array_pop( $stack );
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$stack[] = $v1 >= $v2;
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break;
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case '!=':
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$v2 = array_pop( $stack );
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$v1 = array_pop( $stack );
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$stack[] = $v1 != $v2;
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break;
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case '==':
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$v2 = array_pop( $stack );
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$v1 = array_pop( $stack );
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$stack[] = $v1 == $v2;
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break;
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case '?:':
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$v3 = array_pop( $stack );
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$v2 = array_pop( $stack );
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$v1 = array_pop( $stack );
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$stack[] = $v1 ? $v2 : $v3;
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break;
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default:
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throw new Exception( sprintf( 'Unknown operator "%s"', $next[1] ) );
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}
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}
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if ( count( $stack ) !== 1 ) {
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throw new Exception( 'Too many values remaining on the stack' );
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}
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return (int) $stack[0];
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}
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}
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endif;
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