403 lines
13 KiB
PHP
403 lines
13 KiB
PHP
<?php
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if ( ! defined( 'ABSPATH' ) ) {
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exit;
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}
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if ( ! class_exists( 'WC_Eval_Math', false ) ) {
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/**
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* Class WC_Eval_Math. Supports basic math only (removed eval function).
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*
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* Based on EvalMath by Miles Kaufman Copyright (C) 2005 Miles Kaufmann http://www.twmagic.com/.
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*/
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class WC_Eval_Math {
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/**
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* Last error.
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*
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* @var string
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*/
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public static $last_error = null;
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/**
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* Variables (and constants).
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*
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* @var array
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*/
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public static $v = array( 'e' => 2.71, 'pi' => 3.14 );
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/**
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* User-defined functions.
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*
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* @var array
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*/
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public static $f = array();
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/**
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* Constants.
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*
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* @var array
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*/
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public static $vb = array( 'e', 'pi' );
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/**
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* Built-in functions.
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*
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* @var array
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*/
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public static $fb = array();
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/**
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* Evaluate maths string.
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*
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* @param string $expr
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* @return mixed
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*/
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public static function evaluate( $expr ) {
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self::$last_error = null;
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$expr = trim( $expr );
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if ( substr( $expr, -1, 1 ) == ';' ) {
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$expr = substr( $expr, 0, strlen( $expr ) -1 ); // strip semicolons at the end
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}
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// ===============
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// is it a variable assignment?
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if ( preg_match( '/^\s*([a-z]\w*)\s*=\s*(.+)$/', $expr, $matches ) ) {
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if ( in_array( $matches[1], self::$vb ) ) { // make sure we're not assigning to a constant
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return self::trigger( "cannot assign to constant '$matches[1]'" );
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}
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if ( ( $tmp = self::pfx( self::nfx( $matches[2] ) ) ) === false ) {
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return false; // get the result and make sure it's good
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}
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self::$v[ $matches[1] ] = $tmp; // if so, stick it in the variable array
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return self::$v[ $matches[1] ]; // and return the resulting value
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// ===============
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// is it a function assignment?
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} elseif ( preg_match( '/^\s*([a-z]\w*)\s*\(\s*([a-z]\w*(?:\s*,\s*[a-z]\w*)*)\s*\)\s*=\s*(.+)$/', $expr, $matches ) ) {
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$fnn = $matches[1]; // get the function name
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if ( in_array( $matches[1], self::$fb ) ) { // make sure it isn't built in
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return self::trigger( "cannot redefine built-in function '$matches[1]()'" );
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}
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$args = explode( ",", preg_replace( "/\s+/", "", $matches[2] ) ); // get the arguments
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if ( ( $stack = self::nfx( $matches[3] ) ) === false ) {
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return false; // see if it can be converted to postfix
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}
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$stack_size = count( $stack );
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for ( $i = 0; $i < $stack_size; $i++ ) { // freeze the state of the non-argument variables
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$token = $stack[ $i ];
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if ( preg_match( '/^[a-z]\w*$/', $token ) and ! in_array( $token, $args ) ) {
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if ( array_key_exists( $token, self::$v ) ) {
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$stack[ $i ] = self::$v[ $token ];
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} else {
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return self::trigger( "undefined variable '$token' in function definition" );
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}
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}
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}
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self::$f[ $fnn ] = array( 'args' => $args, 'func' => $stack );
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return true;
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// ===============
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} else {
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return self::pfx( self::nfx( $expr ) ); // straight up evaluation, woo
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}
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}
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/**
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* Convert infix to postfix notation.
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*
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* @param string $expr
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*
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* @return array|string
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*/
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private static function nfx( $expr ) {
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$index = 0;
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$stack = new WC_Eval_Math_Stack;
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$output = array(); // postfix form of expression, to be passed to pfx()
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$expr = trim( $expr );
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$ops = array( '+', '-', '*', '/', '^', '_' );
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$ops_r = array( '+' => 0, '-' => 0, '*' => 0, '/' => 0, '^' => 1 ); // right-associative operator?
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$ops_p = array( '+' => 0, '-' => 0, '*' => 1, '/' => 1, '_' => 1, '^' => 2 ); // operator precedence
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$expecting_op = false; // we use this in syntax-checking the expression
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// and determining when a - is a negation
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if ( preg_match( "/[^\w\s+*^\/()\.,-]/", $expr, $matches ) ) { // make sure the characters are all good
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return self::trigger( "illegal character '{$matches[0]}'" );
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}
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while ( 1 ) { // 1 Infinite Loop ;)
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$op = substr( $expr, $index, 1 ); // get the first character at the current index
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// find out if we're currently at the beginning of a number/variable/function/parenthesis/operand
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$ex = preg_match( '/^([A-Za-z]\w*\(?|\d+(?:\.\d*)?|\.\d+|\()/', substr( $expr, $index ), $match );
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// ===============
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if ( '-' === $op and ! $expecting_op ) { // is it a negation instead of a minus?
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$stack->push( '_' ); // put a negation on the stack
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$index++;
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} elseif ( '_' === $op ) { // we have to explicitly deny this, because it's legal on the stack
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return self::trigger( "illegal character '_'" ); // but not in the input expression
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// ===============
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} elseif ( ( in_array( $op, $ops ) or $ex ) and $expecting_op ) { // are we putting an operator on the stack?
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if ( $ex ) { // are we expecting an operator but have a number/variable/function/opening parenthesis?
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$op = '*';
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$index--; // it's an implicit multiplication
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}
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// heart of the algorithm:
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while ( $stack->count > 0 and ( $o2 = $stack->last() ) and in_array( $o2, $ops ) and ( $ops_r[ $op ] ? $ops_p[ $op ] < $ops_p[ $o2 ] : $ops_p[ $op ] <= $ops_p[ $o2 ] ) ) {
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$output[] = $stack->pop(); // pop stuff off the stack into the output
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}
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// many thanks: https://en.wikipedia.org/wiki/Reverse_Polish_notation#The_algorithm_in_detail
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$stack->push( $op ); // finally put OUR operator onto the stack
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$index++;
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$expecting_op = false;
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// ===============
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} elseif ( ')' === $op && $expecting_op ) { // ready to close a parenthesis?
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while ( ( $o2 = $stack->pop() ) != '(' ) { // pop off the stack back to the last (
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if ( is_null( $o2 ) ) {
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return self::trigger( "unexpected ')'" );
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} else {
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$output[] = $o2;
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}
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}
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if ( preg_match( "/^([A-Za-z]\w*)\($/", $stack->last( 2 ), $matches ) ) { // did we just close a function?
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$fnn = $matches[1]; // get the function name
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$arg_count = $stack->pop(); // see how many arguments there were (cleverly stored on the stack, thank you)
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$output[] = $stack->pop(); // pop the function and push onto the output
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if ( in_array( $fnn, self::$fb ) ) { // check the argument count
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if ( $arg_count > 1 ) {
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return self::trigger( "too many arguments ($arg_count given, 1 expected)" );
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}
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} elseif ( array_key_exists( $fnn, self::$f ) ) {
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if ( count( self::$f[ $fnn ]['args'] ) != $arg_count ) {
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return self::trigger( "wrong number of arguments ($arg_count given, " . count( self::$f[ $fnn ]['args'] ) . " expected)" );
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}
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} else { // did we somehow push a non-function on the stack? this should never happen
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return self::trigger( "internal error" );
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}
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}
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$index++;
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// ===============
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} elseif ( ',' === $op and $expecting_op ) { // did we just finish a function argument?
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while ( ( $o2 = $stack->pop() ) != '(' ) {
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if ( is_null( $o2 ) ) {
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return self::trigger( "unexpected ','" ); // oops, never had a (
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} else {
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$output[] = $o2; // pop the argument expression stuff and push onto the output
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}
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}
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// make sure there was a function
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if ( ! preg_match( "/^([A-Za-z]\w*)\($/", $stack->last( 2 ), $matches ) ) {
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return self::trigger( "unexpected ','" );
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}
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$stack->push( $stack->pop() + 1 ); // increment the argument count
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$stack->push( '(' ); // put the ( back on, we'll need to pop back to it again
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$index++;
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$expecting_op = false;
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// ===============
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} elseif ( '(' === $op and ! $expecting_op ) {
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$stack->push( '(' ); // that was easy
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$index++;
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// ===============
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} elseif ( $ex and ! $expecting_op ) { // do we now have a function/variable/number?
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$expecting_op = true;
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$val = $match[1];
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if ( preg_match( "/^([A-Za-z]\w*)\($/", $val, $matches ) ) { // may be func, or variable w/ implicit multiplication against parentheses...
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if ( in_array( $matches[1], self::$fb ) or array_key_exists( $matches[1], self::$f ) ) { // it's a func
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$stack->push( $val );
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$stack->push( 1 );
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$stack->push( '(' );
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$expecting_op = false;
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} else { // it's a var w/ implicit multiplication
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$val = $matches[1];
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$output[] = $val;
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}
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} else { // it's a plain old var or num
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$output[] = $val;
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}
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$index += strlen( $val );
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// ===============
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} elseif ( ')' === $op ) { // miscellaneous error checking
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return self::trigger( "unexpected ')'" );
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} elseif ( in_array( $op, $ops ) and ! $expecting_op ) {
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return self::trigger( "unexpected operator '$op'" );
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} else { // I don't even want to know what you did to get here
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return self::trigger( "an unexpected error occurred" );
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}
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if ( strlen( $expr ) == $index ) {
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if ( in_array( $op, $ops ) ) { // did we end with an operator? bad.
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return self::trigger( "operator '$op' lacks operand" );
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} else {
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break;
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}
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}
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while ( substr( $expr, $index, 1 ) == ' ' ) { // step the index past whitespace (pretty much turns whitespace
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$index++; // into implicit multiplication if no operator is there)
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}
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}
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while ( ! is_null( $op = $stack->pop() ) ) { // pop everything off the stack and push onto output
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if ( '(' === $op ) {
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return self::trigger( "expecting ')'" ); // if there are (s on the stack, ()s were unbalanced
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}
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$output[] = $op;
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}
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return $output;
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}
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/**
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* Evaluate postfix notation.
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*
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* @param mixed $tokens
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* @param array $vars
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*
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* @return mixed
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*/
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private static function pfx( $tokens, $vars = array() ) {
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if ( false == $tokens ) {
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return false;
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}
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$stack = new WC_Eval_Math_Stack;
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foreach ( $tokens as $token ) { // nice and easy
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// if the token is a binary operator, pop two values off the stack, do the operation, and push the result back on
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if ( in_array( $token, array( '+', '-', '*', '/', '^' ) ) ) {
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if ( is_null( $op2 = $stack->pop() ) ) {
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return self::trigger( "internal error" );
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}
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if ( is_null( $op1 = $stack->pop() ) ) {
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return self::trigger( "internal error" );
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}
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switch ( $token ) {
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case '+':
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$stack->push( $op1 + $op2 );
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break;
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case '-':
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$stack->push( $op1 - $op2 );
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break;
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case '*':
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$stack->push( $op1 * $op2 );
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break;
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case '/':
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if ( 0 == $op2 ) {
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return self::trigger( 'division by zero' );
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}
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$stack->push( $op1 / $op2 );
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break;
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case '^':
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$stack->push( pow( $op1, $op2 ) );
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break;
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}
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// if the token is a unary operator, pop one value off the stack, do the operation, and push it back on
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} elseif ( '_' === $token ) {
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$stack->push( -1 * $stack->pop() );
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// if the token is a function, pop arguments off the stack, hand them to the function, and push the result back on
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} elseif ( ! preg_match( "/^([a-z]\w*)\($/", $token, $matches ) ) {
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if ( is_numeric( $token ) ) {
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$stack->push( $token );
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} elseif ( array_key_exists( $token, self::$v ) ) {
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$stack->push( self::$v[ $token ] );
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} elseif ( array_key_exists( $token, $vars ) ) {
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$stack->push( $vars[ $token ] );
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} else {
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return self::trigger( "undefined variable '$token'" );
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}
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}
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}
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// when we're out of tokens, the stack should have a single element, the final result
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if ( 1 != $stack->count ) {
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return self::trigger( "internal error" );
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}
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return $stack->pop();
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}
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/**
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* Trigger an error, but nicely, if need be.
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*
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* @param string $msg
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*
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* @return bool
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*/
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private static function trigger( $msg ) {
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self::$last_error = $msg;
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if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
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echo "\nError found in:";
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self::debugPrintCallingFunction();
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trigger_error( $msg, E_USER_WARNING );
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}
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return false;
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}
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/**
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* Prints the file name, function name, and
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* line number which called your function
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* (not this function, then one that called
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* it to begin with)
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*/
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private static function debugPrintCallingFunction() {
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$file = 'n/a';
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$func = 'n/a';
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$line = 'n/a';
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$debugTrace = debug_backtrace();
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if ( isset( $debugTrace[1] ) ) {
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$file = $debugTrace[1]['file'] ? $debugTrace[1]['file'] : 'n/a';
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$line = $debugTrace[1]['line'] ? $debugTrace[1]['line'] : 'n/a';
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}
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if ( isset( $debugTrace[2] ) ) {
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$func = $debugTrace[2]['function'] ? $debugTrace[2]['function'] : 'n/a';
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}
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echo "\n$file, $func, $line\n";
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}
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}
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/**
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* Class WC_Eval_Math_Stack.
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*/
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class WC_Eval_Math_Stack {
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/**
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* Stack array.
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*
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* @var array
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*/
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public $stack = array();
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/**
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* Stack counter.
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*
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* @var integer
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*/
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public $count = 0;
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/**
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* Push value into stack.
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*
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* @param mixed $val
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*/
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public function push( $val ) {
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$this->stack[ $this->count ] = $val;
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$this->count++;
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}
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/**
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* Pop value from stack.
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*
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* @return mixed
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*/
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public function pop() {
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if ( $this->count > 0 ) {
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$this->count--;
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return $this->stack[ $this->count ];
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}
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return null;
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}
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/**
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* Get last value from stack.
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*
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* @param int $n
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*
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* @return mixed
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*/
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public function last( $n=1 ) {
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$key = $this->count - $n;
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return array_key_exists( $key, $this->stack ) ? $this->stack[ $key ] : null;
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}
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}
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}
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