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343 lines
6.8 KiB
343 lines
6.8 KiB
<?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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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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* @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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return $this->cache[ $num ] = $this->execute( $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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* @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 ( $next[0] === 'var' ) { |
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$stack[] = $n; |
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continue; |
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} elseif ( $next[0] === 'value' ) { |
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$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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