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<?php

/**

 * @file

 * =============================================================================.

 *

 * ctools_math_expr - PHP Class to safely evaluate math expressions

 * Copyright (C) 2005 Miles Kaufmann <http://www.twmagic.com/>

 *

 * =============================================================================

 *

 * NAME

 *     ctools_math_expr - safely evaluate math expressions

 *

 * SYNOPSIS

 *     $m = new ctools_math_expr();

 *     // basic evaluation:

 *     $result = $m->evaluate('2+2');

 *     // supports: order of operation; parentheses; negation; built-in

 *     // functions.

 *     $result = $m->evaluate('-8(5/2)^2*(1-sqrt(4))-8');

 *     // create your own variables

 *     $m->evaluate('a = e^(ln(pi))');

 *     // or functions

 *     $m->evaluate('f(x,y) = x^2 + y^2 - 2x*y + 1');

 *     // and then use them

 *     $result = $m->evaluate('3*f(42,a)');

 *

 * DESCRIPTION

 *     Use the ctools_math_expr class when you want to evaluate mathematical

 *     expressions from untrusted sources.  You can define your own variables

 *     and functions, which are stored in the object.  Try it, it's fun!

 *

 * AUTHOR INFORMATION

 *     Copyright 2005, Miles Kaufmann.

 *     Enhancements, 2005 onwards, Drupal Community.

 *

 * LICENSE

 *     Redistribution and use in source and binary forms, with or without

 *     modification, are permitted provided that the following conditions are

 *     met:

 *

 *     1   Redistributions of source code must retain the above copyright

 *         notice, this list of conditions and the following disclaimer.

 *     2.  Redistributions in binary form must reproduce the above copyright

 *         notice, this list of conditions and the following disclaimer in the

 *         documentation and/or other materials provided with the distribution.

 *     3.  The name of the author may not be used to endorse or promote

 *         products derived from this software without specific prior written

 *         permission.

 *

 *     THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 *     IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 *     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 *     DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,

 *     INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 *     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

 *     SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 *     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

 *     STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN

 *     ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

 *     POSSIBILITY OF SUCH DAMAGE.

 */

/**

 * ctools_math_expr Class.

 */

class ctools_math_expr {

  /**

   * If TRUE do not call trigger_error on error other wise do.

   *

   * @var bool

   */

  public $suppress_errors = FALSE;

  /**

   * The last error message reported.

   *

   * @var string

   */

  public $last_error = NULL;

  /**

   * List of all errors reported.

   *

   * @var array

   */

  public $errors = array();

  /**

   * Variable and constant values.

   *

   * @var array

   */

  protected $vars;

  /**

   * User defined functions.

   *

   * @var array

   */

  protected $userfuncs;

  /**

   * The names of constants, used to make constants read-only.

   *

   * @var array

   */

  protected $constvars;

  /**

   * Built in simple (one arg) functions.

   * Merged into $this->funcs in constructor.

   *

   * @var array

   */

  protected $simplefuncs;

  /**

   * Definitions of all built-in functions.

   *

   * @var array

   */

  protected $funcs;

  /**

   * Operators and their precedence.

   *

   * @var array

   */

  protected $ops;

  /**

   * The set of operators using two arguments.

   *

   * @var array

   */

  protected $binaryops;

  /**

   * Public constructor.

   */

  public function __construct() {

    $this->userfuncs = array();

    $this->simplefuncs = array(

      'sin',

      'sinh',

      'asin',

      'asinh',

      'cos',

      'cosh',

      'acos',

      'acosh',

      'tan',

      'tanh',

      'atan',

      'atanh',

      'exp',

      'sqrt',

      'abs',

      'log',

      'ceil',

      'floor',

      'round',

    );

    $this->ops = array(

      '+' => array('precedence' => 0),

      '-' => array('precedence' => 0),

      '*' => array('precedence' => 1),

      '/' => array('precedence' => 1),

      '^' => array('precedence' => 2, 'right' => TRUE),

      '_' => array('precedence' => 1),

      '==' => array('precedence' => -1),

      '!=' => array('precedence' => -1),

      '>=' => array('precedence' => -1),

      '<=' => array('precedence' => -1),

      '>' => array('precedence' => -1),

      '<' => array('precedence' => -1),

    );

    $this->binaryops = array(

      '+', '-', '*', '/', '^', '==', '!=', '<', '<=', '>=', '>',

    );

    $this->funcs = array(

      'ln' => array(

        'function' => 'log',

        'arguments' => 1,

      ),

      'arcsin' => array(

        'function' => 'asin',

        'arguments' => 1,

      ),

      'arcsinh' => array(

        'function' => 'asinh',

        'arguments' => 1,

      ),

      'arccos' => array(

        'function' => 'acos',

        'arguments' => 1,

      ),

      'arccosh' => array(

        'function' => 'acosh',

        'arguments' => 1,

      ),

      'arctan' => array(

        'function' => 'atan',

        'arguments' => 1,

      ),

      'arctanh' => array(

        'function' => 'atanh',

        'arguments' => 1,

      ),

      'min' => array(

        'function' => 'min',

        'arguments' => 2,

        'max arguments' => 99,

      ),

      'max' => array(

        'function' => 'max',

        'arguments' => 2,

        'max arguments' => 99,

      ),

      'pow' => array(

        'function' => 'pow',

        'arguments' => 2,

      ),

      'if' => array(

        'function' => 'ctools_math_expr_if',

        'arguments' => 2,

        'max arguments' => 3,

      ),

      'number' => array(

        'function' => 'ctools_math_expr_number',

        'arguments' => 1,

      ),

      'time' => array(

        'function' => 'time',

        'arguments' => 0,

      ),

    );

    // Allow modules to add custom functions.

    $context = array('final' => &$this->funcs);

    drupal_alter('ctools_math_expression_functions', $this->simplefuncs, $context);

    // Set up the initial constants and mark them read-only.

    $this->vars = array('e' => exp(1), 'pi' => pi());

    drupal_alter('ctools_math_expression_constants', $this->vars);

    $this->constvars = array_keys($this->vars);

    // Translate the older, simpler style into the newer, richer style.

    foreach ($this->simplefuncs as $function) {

      $this->funcs[$function] = array(

        'function' => $function,

        'arguments' => 1,

      );

    }

  }

  /**

   * Change the suppress errors flag.

   *

   * When errors are not suppressed, trigger_error is used to cause a PHP error

   * when an evaluation error occurs, as a result of calling trigger(). With

   * errors suppressed this doesn't happen.

   *

   * @param bool $enable

   *   If FALSE, enable triggering of php errors when expression errors occurs.

   *   otherwise, suppress triggering the errors.

   *

   * @return bool

   *   The new (current) state of the flag.

   *

   * @see ctools_math_expr::trigger()

   */

  public function set_suppress_errors($enable) {

    return $this->suppress_errors = (bool) $enable;

  }

  /**

   * Backwards compatible wrapper for evaluate().

   *

   * @see ctools_math_expr::evaluate()

   */

  public function e($expr) {

    return $this->evaluate($expr);

  }

  /**

   * Evaluate the expression.

   *

   * @param string $expr

   *   The expression to evaluate.

   *

   * @return string|bool

   *   The result of the expression, or FALSE if an error occurred, or TRUE if

   *   an user-defined function was created.

   */

  public function evaluate($expr) {

    $this->last_error = NULL;

    $expr = trim($expr);

    // Strip possible semicolons at the end.

    if (substr($expr, -1, 1) == ';') {

      $expr = substr($expr, 0, -1);

    }

    // Is it a variable assignment?

    if (preg_match('/^\s*([a-z]\w*)\s*=\s*(.+)$/', $expr, $matches)) {

      // Make sure we're not assigning to a constant.

      if (in_array($matches[1], $this->constvars)) {

        return $this->trigger("cannot assign to constant '$matches[1]'");

      }

      // Get the result and make sure it's good:

      if (($tmp = $this->pfx($this->nfx($matches[2]))) === FALSE) {

        return FALSE;

      }

      // If so, stick it in the variable array...

      $this->vars[$matches[1]] = $tmp;

      // ...and return the resulting value:

      return $this->vars[$matches[1]];

    }

    // Is it a function assignment?

    elseif (preg_match('/^\s*([a-z]\w*)\s*\(\s*([a-z]\w*(?:\s*,\s*[a-z]\w*)*)\s*\)\s*=\s*(.+)$/', $expr, $matches)) {

      // Get the function name.

      $fnn = $matches[1];

      // Make sure it isn't built in:

      if (isset($this->funcs[$matches[1]])) {

        return $this->trigger("cannot redefine built-in function '$matches[1]()'");

      }

      // Get the arguments.

      $args = explode(",", preg_replace("/\s+/", "", $matches[2]));

      // See if it can be converted to postfix.

      $stack = $this->nfx($matches[3]);

      if ($stack === FALSE) {

        return FALSE;

      }

      // Freeze the state of the non-argument variables.

      for ($i = 0; $i < count($stack); $i++) {

        $token = $stack[$i];

        if (preg_match('/^[a-z]\w*$/', $token) and !in_array($token, $args)) {

          if (array_key_exists($token, $this->vars)) {

            $stack[$i] = $this->vars[$token];

          }

          else {

            return $this->trigger("undefined variable '$token' in function definition");

          }

        }

      }

      $this->userfuncs[$fnn] = array('args' => $args, 'func' => $stack);

      return TRUE;

    }

    else {

      // Straight up evaluation.

      return trim($this->pfx($this->nfx($expr)), '"');

    }

  }

  /**

   * Fetch an array of variables used in the expression.

   *

   * @return array

   *   Array of name : value pairs, one for each variable defined.

   */

  public function vars() {

    $output = $this->vars;

    // @todo: Is this supposed to remove all constants? we should remove all

    // those in $this->constvars!

    unset($output['pi']);

    unset($output['e']);

    return $output;

  }

  /**

   * Fetch all user defined functions in the expression.

   *

   * @return array

   *   Array of name : string pairs, one for each function defined. The string

   *   will be of the form fname(arg1,arg2). The function body is not returned.

   */

  public function funcs() {

    $output = array();

    foreach ($this->userfuncs as $fnn => $dat) {

      $output[] = $fnn . '(' . implode(',', $dat['args']) . ')';

    }

    return $output;

  }

  /**

   * Convert infix to postfix notation.

   *

   * @param string $expr

   *   The expression to convert.

   *

   * @return array|bool

   *   The expression as an ordered list of postfix action tokens.

   */

  private function nfx($expr) {

    $index = 0;

    $stack = new ctools_math_expr_stack();

    // Postfix form of expression, to be passed to pfx().

    $output = array();

    // @todo: Because the expr can contain string operands, using strtolower here is a bug.

    $expr = trim(strtolower($expr));

    // We use this in syntax-checking the expression and determining when

    // '-' is a negation.

    $expecting_op = FALSE;

    while (TRUE) {

      $op = substr($expr, $index, 1);

      // Get the first character at the current index, and if the second

      // character is an =, add it to our op as well (accounts for <=).

      if (substr($expr, $index + 1, 1) === '=') {

        $op = substr($expr, $index, 2);

        $index++;

      }

      // Find out if we're currently at the beginning of a number/variable/

      // function/parenthesis/operand.

      $ex = preg_match('/^([a-z]\w*\(?|\d+(?:\.\d*)?|\.\d+|\()/', substr($expr, $index), $match);

      // Is it a negation instead of a minus?

      if ($op === '-' and !$expecting_op) {

        // Put a negation on the stack.

        $stack->push('_');

        $index++;

      }

      // We have to explicitly deny this, because it's legal on the stack but

      // not in the input expression.

      elseif ($op == '_') {

        return $this->trigger("illegal character '_'");

      }

      // Are we putting an operator on the stack?

      elseif ((isset($this->ops[$op]) || $ex) && $expecting_op) {

        // Are we expecting an operator but have a num, var, func, or

        // open-paren?

        if ($ex) {

          $op = '*';

          // It's an implicit multiplication.

          $index--;

        }

        // Heart of the algorithm:

        while ($stack->count() > 0 &&

          ($o2 = $stack->last()) &&

          isset($this->ops[$o2]) &&

          (!empty($this->ops[$op]['right']) ?

            $this->ops[$op]['precedence'] < $this->ops[$o2]['precedence'] :

            $this->ops[$op]['precedence'] <= $this->ops[$o2]['precedence'])) {

          // Pop stuff off the stack into the output.

          $output[] = $stack->pop();

        }

        // Many thanks: http://en.wikipedia.org/wiki/Reverse_Polish_notation#The_algorithm_in_detail

        // finally put OUR operator onto the stack.

        $stack->push($op);

        $index++;

        $expecting_op = FALSE;

      }

      // Ready to close a parenthesis?

      elseif ($op === ')') {

        // Pop off the stack back to the last '('.

        while (($o2 = $stack->pop()) !== '(') {

          if (is_null($o2)) {

            return $this->trigger("unexpected ')'");

          }

          else {

            $output[] = $o2;

          }

        }

        // Did we just close a function?

        if (preg_match("/^([a-z]\w*)\($/", $stack->last(2), $matches)) {

          // Get the function name.

          $fnn = $matches[1];

          // See how many arguments there were (cleverly stored on the stack,

          // thank you).

          $arg_count = $stack->pop();

          // Pop the function and push onto the output.

          $output[] = $stack->pop();

          // Check the argument count:

          if (isset($this->funcs[$fnn])) {

            $fdef = $this->funcs[$fnn];

            $max_arguments = isset($fdef['max arguments']) ? $fdef['max arguments'] : $fdef['arguments'];

            if ($arg_count > $max_arguments) {

              return $this->trigger("too many arguments ($arg_count given, $max_arguments expected)");

            }

          }

          elseif (array_key_exists($fnn, $this->userfuncs)) {

            $fdef = $this->userfuncs[$fnn];

            if ($arg_count !== count($fdef['args'])) {

              return $this->trigger("wrong number of arguments ($arg_count given, " . count($fdef['args']) . ' expected)');

            }

          }

          else {

            // Did we somehow push a non-function on the stack? this should

            // never happen.

            return $this->trigger('internal error');

          }

        }

        $index++;

      }

      // Did we just finish a function argument?

      elseif ($op === ',' && $expecting_op) {

        $index++;

        $expecting_op = FALSE;

      }

      elseif ($op === '(' && !$expecting_op) {

        $stack->push('(');

        $index++;

      }

      elseif ($ex && !$expecting_op) {

        // Make sure there was a function.

        if (preg_match("/^([a-z]\w*)\($/", $stack->last(3), $matches)) {

          // Pop the argument expression stuff and push onto the output:

          while (($o2 = $stack->pop()) !== '(') {

            // Oops, never had a '('.

            if (is_null($o2)) {

              return $this->trigger("unexpected argument in $expr $o2");

            }

            else {

              $output[] = $o2;

            }

          }

          // Increment the argument count.

          $stack->push($stack->pop() + 1);

          // Put the ( back on, we'll need to pop back to it again.

          $stack->push('(');

        }

        // Do we now have a function/variable/number?

        $expecting_op = TRUE;

        $val = $match[1];

        if (preg_match("/^([a-z]\w*)\($/", $val, $matches)) {

          // May be func, or variable w/ implicit multiplication against

          // parentheses...

          if (isset($this->funcs[$matches[1]]) or array_key_exists($matches[1], $this->userfuncs)) {

            $stack->push($val);

            $stack->push(0);

            $stack->push('(');

            $expecting_op = FALSE;

          }

          // it's a var w/ implicit multiplication.

          else {

            $val = $matches[1];

            $output[] = $val;

          }

        }

        // it's a plain old var or num.

        else {

          $output[] = $val;

        }

        $index += strlen($val);

      }

      elseif ($op === ')') {

        // Miscellaneous error checking.

        return $this->trigger("unexpected ')'");

      }

      elseif (isset($this->ops[$op]) and !$expecting_op) {

        return $this->trigger("unexpected operator '$op'");

      }

      elseif ($op === '"') {

        // Fetch a quoted string.

        $string = substr($expr, $index);

        if (preg_match('/"[^"\\\\]*(?:\\\\.[^"\\\\]*)*"/s', $string, $matches)) {

          $string = $matches[0];

          // Trim the quotes off:

          $output[] = $string;

          $index += strlen($string);

          $expecting_op = TRUE;

        }

        else {

          return $this->trigger('open quote without close quote.');

        }

      }

      else {

        // I don't even want to know what you did to get here.

        return $this->trigger("an unexpected error occurred at $op");

      }

      if ($index === strlen($expr)) {

        if (isset($this->ops[$op])) {

          // Did we end with an operator? bad.

          return $this->trigger("operator '$op' lacks operand");

        }

        else {

          break;

        }

      }

      // Step the index past whitespace (pretty much turns whitespace into

      // implicit multiplication if no operator is there).

      while (substr($expr, $index, 1) === ' ') {

        $index++;

      }

    }

    // Pop everything off the stack and push onto output:

    while (!is_null($op = $stack->pop())) {

      // If there are (s on the stack, ()s were unbalanced.

      if ($op === '(') {

        return $this->trigger("expecting ')'");

      }

      $output[] = $op;

    }

    return $output;

  }

  /**

   * Evaluate a prefix-operator stack expression.

   *

   * @param array $tokens

   *   The array of token values to evaluate. A token is a string value

   *   representing either an operation to perform, a variable, or a value.

   *   Literal values are checked using is_numeric(), or a value that starts

   *   with a double-quote; functions and variables by existence in the

   *   appropriate tables.

   *   If FALSE is passed in the function terminates immediately, returning

   *   FALSE.

   * @param array $vars

   *   Additional variable values to use when evaluating the expression. These

   *   variables do not override internal variables with the same name.

   *

   * @return bool|mixed

   *   The expression's value, otherwise FALSE is returned if there is an error

   *   detected unless php error handling intervenes: see suppress_error.

   */

  public function pfx(array $tokens, array $vars = array()) {

    if ($tokens == FALSE) {

      return FALSE;

    }

    $stack = new ctools_math_expr_stack();

    foreach ($tokens as $token) {

      // If the token is a binary operator, pop two values off the stack, do

      // the operation, and push the result back on again.

      if (in_array($token, $this->binaryops)) {

        if (is_null($op2 = $stack->pop())) {

          return $this->trigger('internal error');

        }

        if (is_null($op1 = $stack->pop())) {

          return $this->trigger('internal error');

        }

        switch ($token) {

          case '+':

            $stack->push($op1 + $op2);

            break;

          case '-':

            $stack->push($op1 - $op2);

            break;

          case '*':

            $stack->push($op1 * $op2);

            break;

          case '/':

            if ($op2 == 0) {

              return $this->trigger('division by zero');

            }

            $stack->push($op1 / $op2);

            break;

          case '^':

            $stack->push(pow($op1, $op2));

            break;

          case '==':

            $stack->push((int) ($op1 == $op2));

            break;

          case '!=':

            $stack->push((int) ($op1 != $op2));

            break;

          case '<=':

            $stack->push((int) ($op1 <= $op2));

            break;

          case '<':

            $stack->push((int) ($op1 < $op2));

            break;

          case '>=':

            $stack->push((int) ($op1 >= $op2));

            break;

          case '>':

            $stack->push((int) ($op1 > $op2));

            break;

        }

      }

      // If the token is a unary operator, pop one value off the stack, do the

      // operation, and push it back on again.

      elseif ($token === "_") {

        $stack->push(-1 * $stack->pop());

      }

      // If the token is a function, pop arguments off the stack, hand them to

      // the function, and push the result back on again.

      elseif (preg_match("/^([a-z]\w*)\($/", $token, $matches)) {

        $fnn = $matches[1];

        // Check for a built-in function.

        if (isset($this->funcs[$fnn])) {

          $args = array();

          // Collect all required args from the stack.

          for ($i = 0; $i < $this->funcs[$fnn]['arguments']; $i++) {

            if (is_null($op1 = $stack->pop())) {

              return $this->trigger("function $fnn missing argument $i");

            }

            $args[] = $op1;

          }

          // If func allows additional args, collect them too, stopping on a

          // NULL arg.

          if (!empty($this->funcs[$fnn]['max arguments'])) {

            for (; $i < $this->funcs[$fnn]['max arguments']; $i++) {

              $arg = $stack->pop();

              if (!isset($arg)) {

                break;

              }

              $args[] = $arg;

            }

          }

          $stack->push(

            call_user_func_array($this->funcs[$fnn]['function'], array_reverse($args))

          );

        }

        // Check for a user function.

        elseif (isset($fnn, $this->userfuncs)) {

          $args = array();

          for ($i = count($this->userfuncs[$fnn]['args']) - 1; $i >= 0; $i--) {

            $value = $stack->pop();

            $args[$this->userfuncs[$fnn]['args'][$i]] = $value;

            if (is_null($value)) {

              return $this->trigger('internal error');

            }

          }

          // yay... recursion!!!!

          $stack->push($this->pfx($this->userfuncs[$fnn]['func'], $args));

        }

      }

      // If the token is a number or variable, push it on the stack.

      else {

        if (is_numeric($token) || $token[0] == '"') {

          $stack->push($token);

        }

        elseif (array_key_exists($token, $this->vars)) {

          $stack->push($this->vars[$token]);

        }

        elseif (array_key_exists($token, $vars)) {

          $stack->push($vars[$token]);

        }

        else {

          return $this->trigger("undefined variable '$token'");

        }

      }

    }

    // When we're out of tokens, the stack should have a single element, the

    // final result:

    if ($stack->count() !== 1) {

      return $this->trigger('internal error');

    }

    return $stack->pop();

  }

  /**

   * Trigger an error, but nicely, if need be.

   *

   * @param string $msg

   *   Message to add to trigger error.

   *

   * @return bool

   *   Can trigger error, then returns FALSE.

   */

  protected function trigger($msg) {

    $this->errors[] = $msg;

    $this->last_error = $msg;

    if (!$this->suppress_errors) {

      trigger_error($msg, E_USER_WARNING);

    }

    return FALSE;

  }

}

/**

 * Class implementing a simple stack structure, used by ctools_math_expr.

 */

class ctools_math_expr_stack {

  /**

   * The stack.

   *

   * @var array

   */

  private $stack;

  /**

   * The stack pointer, points at the first empty space.

   *

   * @var int

   */

  private $count;

  /**

   * Ctools_math_expr_stack constructor.

   */

  public function __construct() {

    $this->stack = array();

    $this->count = 0;

  }

  /**

   * Push the value onto the stack.

   *

   * @param mixed $val

   */

  public function push($val) {

    $this->stack[$this->count] = $val;

    $this->count++;

  }

  /**

   * Remove the most recently pushed value and return it.

   *

   * @return mixed|null

   *   The most recently pushed value, or NULL if the stack was empty.

   */

  public function pop() {

    if ($this->count > 0) {

      $this->count--;

      return $this->stack[$this->count];

    }

    return NULL;

  }

  /**

   * "Peek" the stack, or Return a value from the stack without removing it.

   *

   * @param int $n

   *   Integer indicating which value to return. 1 is the topmost (i.e. the

   *   value that pop() would return), 2 indicates the next, 3 the third, etc.

   *

   * @return mixed|null

   *   A value pushed onto the stack at the nth position, or NULL if the stack

   *   was empty.

   */

  public function last($n = 1) {

    return !empty($this->stack[$this->count - $n]) ? $this->stack[$this->count - $n] : NULL;

  }

  /**

   * Return the number of items on the stack.

   *

   * @return int

   *   The number of items.

   */

  public function count() {

    return $this->count;

  }

}

/**

 * Helper function for evaluating 'if' condition.

 *

 * @param int $expr

 *   The expression to test: if <> 0 then the $if expression is returned.

 * @param mixed $if

 *   The expression returned if the condition is true.

 * @param mixed $else

 *   Optional. The expression returned if the expression is false.

 *

 * @return mixed|null

 *   The result. NULL is returned when an If condition is False and no Else

 *   expression is provided.

 */

function ctools_math_expr_if($expr, $if, $else = NULL) {

  return $expr ? $if : $else;

}

/**

 * Remove any non-digits so that numbers like $4,511.23 still work.

 *

 * It might be good for those using the 12,345.67 format, but is awful for

 * those using other conventions.

 * Use of the php 'intl' module might work here, if the correct locale can be

 * derived, but that seems unlikely to be true in all cases.

 *

 * @todo: locale could break this since in some locales that's $4.512,33 so

 * there needs to be a way to detect that and make it work properly.

 *

 * @param mixed $arg

 *   A number string with possible leading chars.

 *

 * @return mixed

 *   Returns a number string.

 */

function ctools_math_expr_number($arg) {

  // @todo: A really bad idea: It might be good for those using the 12,345.67

  // format, but is awful for those using other conventions.

  // $arg = preg_replace("/[^0-9\.]/", '', $arg);.

  return $arg;

}