Plural_Forms::execute() WordPress Method

		public function execute( $n ) {
			$stack = array();
			$i     = 0;
			$total = count( $this->tokens );
			while ( $i < $total ) {
				$next = $this->tokens[ $i ];
				$i++;
				if ( 'var' === $next[0] ) {
					$stack[] = $n;
					continue;
				} elseif ( 'value' === $next[0] ) {
					$stack[] = $next[1];
					continue;
				}

				// Only operators left.
				switch ( $next[1] ) {
					case '%':
						$v2      = array_pop( $stack );
						$v1      = array_pop( $stack );
						$stack[] = $v1 % $v2;
						break;

					case '||':
						$v2      = array_pop( $stack );
						$v1      = array_pop( $stack );
						$stack[] = $v1 || $v2;
						break;

					case '&&':
						$v2      = array_pop( $stack );
						$v1      = array_pop( $stack );
						$stack[] = $v1 && $v2;
						break;

					case '<':
						$v2      = array_pop( $stack );
						$v1      = array_pop( $stack );
						$stack[] = $v1 < $v2;
						break;

					case '<=':
						$v2      = array_pop( $stack );
						$v1      = array_pop( $stack );
						$stack[] = $v1 <= $v2;
						break;

					case '>':
						$v2      = array_pop( $stack );
						$v1      = array_pop( $stack );
						$stack[] = $v1 > $v2;
						break;

					case '>=':
						$v2      = array_pop( $stack );
						$v1      = array_pop( $stack );
						$stack[] = $v1 >= $v2;
						break;

					case '!=':
						$v2      = array_pop( $stack );
						$v1      = array_pop( $stack );
						$stack[] = $v1 != $v2;
						break;

					case '==':
						$v2      = array_pop( $stack );
						$v1      = array_pop( $stack );
						$stack[] = $v1 == $v2;
						break;

					case '?:':
						$v3      = array_pop( $stack );
						$v2      = array_pop( $stack );
						$v1      = array_pop( $stack );
						$stack[] = $v1 ? $v2 : $v3;
						break;

					default:
						throw new Exception( sprintf( 'Unknown operator "%s"', $next[1] ) );
				}
			}

			if ( count( $stack ) !== 1 ) {
				throw new Exception( 'Too many values remaining on the stack' );
			}

			return (int) $stack[0];
		}