Plural_Forms::parse( string $str )
Parse a Plural-Forms string into tokens.
Description
Uses the shunting-yard algorithm to convert the string to Reverse Polish Notation tokens.
Parameters
- $str
-
(Required) String to parse.
Source
File: wp-includes/pomo/plural-forms.php
protected function parse( $str ) {
$pos = 0;
$len = strlen( $str );
// Convert infix operators to postfix using the shunting-yard algorithm.
$output = array();
$stack = array();
while ( $pos < $len ) {
$next = substr( $str, $pos, 1 );
switch ( $next ) {
// Ignore whitespace
case ' ':
case "\t":
$pos++;
break;
// Variable (n)
case 'n':
$output[] = array( 'var' );
$pos++;
break;
// Parentheses
case '(':
$stack[] = $next;
$pos++;
break;
case ')':
$found = false;
while ( ! empty( $stack ) ) {
$o2 = $stack[ count( $stack ) - 1 ];
if ( $o2 !== '(' ) {
$output[] = array( 'op', array_pop( $stack ) );
continue;
}
// Discard open paren.
array_pop( $stack );
$found = true;
break;
}
if ( ! $found ) {
throw new Exception( 'Mismatched parentheses' );
}
$pos++;
break;
// Operators
case '|':
case '&':
case '>':
case '<':
case '!':
case '=':
case '%':
case '?':
$end_operator = strspn( $str, self::OP_CHARS, $pos );
$operator = substr( $str, $pos, $end_operator );
if ( ! array_key_exists( $operator, self::$op_precedence ) ) {
throw new Exception( sprintf( 'Unknown operator "%s"', $operator ) );
}
while ( ! empty( $stack ) ) {
$o2 = $stack[ count( $stack ) - 1 ];
// Ternary is right-associative in C
if ( $operator === '?:' || $operator === '?' ) {
if ( self::$op_precedence[ $operator ] >= self::$op_precedence[ $o2 ] ) {
break;
}
} elseif ( self::$op_precedence[ $operator ] > self::$op_precedence[ $o2 ] ) {
break;
}
$output[] = array( 'op', array_pop( $stack ) );
}
$stack[] = $operator;
$pos += $end_operator;
break;
// Ternary "else"
case ':':
$found = false;
$s_pos = count( $stack ) - 1;
while ( $s_pos >= 0 ) {
$o2 = $stack[ $s_pos ];
if ( $o2 !== '?' ) {
$output[] = array( 'op', array_pop( $stack ) );
$s_pos--;
continue;
}
// Replace.
$stack[ $s_pos ] = '?:';
$found = true;
break;
}
if ( ! $found ) {
throw new Exception( 'Missing starting "?" ternary operator' );
}
$pos++;
break;
// Default - number or invalid
default:
if ( $next >= '0' && $next <= '9' ) {
$span = strspn( $str, self::NUM_CHARS, $pos );
$output[] = array( 'value', intval( substr( $str, $pos, $span ) ) );
$pos += $span;
break;
}
throw new Exception( sprintf( 'Unknown symbol "%s"', $next ) );
}
}
while ( ! empty( $stack ) ) {
$o2 = array_pop( $stack );
if ( $o2 === '(' || $o2 === ')' ) {
throw new Exception( 'Mismatched parentheses' );
}
$output[] = array( 'op', $o2 );
}
$this->tokens = $output;
}
Changelog
Version | Description |
---|---|
WP-4.9.0 | Introduced. |