934 lines
26 KiB
PHP
934 lines
26 KiB
PHP
<?php
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/**
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* @file
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* =============================================================================.
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*
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* ctools_math_expr - PHP Class to safely evaluate math expressions
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* Copyright (C) 2005 Miles Kaufmann <http://www.twmagic.com/>
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*
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* =============================================================================
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*
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* NAME
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* ctools_math_expr - safely evaluate math expressions
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*
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* SYNOPSIS
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* $m = new ctools_math_expr();
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* // basic evaluation:
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* $result = $m->evaluate('2+2');
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* // supports: order of operation; parentheses; negation; built-in
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* // functions.
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* $result = $m->evaluate('-8(5/2)^2*(1-sqrt(4))-8');
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* // create your own variables
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* $m->evaluate('a = e^(ln(pi))');
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* // or functions
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* $m->evaluate('f(x,y) = x^2 + y^2 - 2x*y + 1');
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* // and then use them
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* $result = $m->evaluate('3*f(42,a)');
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*
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* DESCRIPTION
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* Use the ctools_math_expr class when you want to evaluate mathematical
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* expressions from untrusted sources. You can define your own variables
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* and functions, which are stored in the object. Try it, it's fun!
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*
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* AUTHOR INFORMATION
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* Copyright 2005, Miles Kaufmann.
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* Enhancements, 2005 onwards, Drupal Community.
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*
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* LICENSE
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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*
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* 1 Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/**
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* ctools_math_expr Class.
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*/
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class ctools_math_expr {
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/**
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* If TRUE do not call trigger_error on error other wise do.
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*
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* @var bool
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*/
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public $suppress_errors = FALSE;
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/**
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* The last error message reported.
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*
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* @var string
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*/
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public $last_error = NULL;
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/**
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* List of all errors reported.
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*
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* @var array
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*/
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public $errors = array();
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/**
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* Variable and constant values.
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*
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* @var array
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*/
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protected $vars;
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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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protected $userfuncs;
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/**
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* The names of constants, used to make constants read-only.
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*
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* @var array
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*/
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protected $constvars;
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/**
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* Built in simple (one arg) functions.
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* Merged into $this->funcs in constructor.
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*
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* @var array
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*/
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protected $simplefuncs;
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/**
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* Definitions of all built-in functions.
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*
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* @var array
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*/
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protected $funcs;
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/**
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* Operators and their precedence.
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*
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* @var array
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*/
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protected $ops;
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/**
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* The set of operators using two arguments.
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*
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* @var array
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*/
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protected $binaryops;
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/**
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* Public constructor.
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*/
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public function __construct() {
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$this->userfuncs = array();
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$this->simplefuncs = array(
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'sin',
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'sinh',
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'asin',
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'asinh',
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'cos',
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'cosh',
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'acos',
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'acosh',
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'tan',
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'tanh',
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'atan',
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'atanh',
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'exp',
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'sqrt',
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'abs',
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'log',
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'ceil',
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'floor',
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'round',
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);
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$this->ops = array(
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'+' => array('precedence' => 0),
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'-' => array('precedence' => 0),
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'*' => array('precedence' => 1),
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'/' => array('precedence' => 1),
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'^' => array('precedence' => 2, 'right' => TRUE),
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'_' => array('precedence' => 1),
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'==' => array('precedence' => -1),
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'!=' => array('precedence' => -1),
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'>=' => array('precedence' => -1),
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'<=' => array('precedence' => -1),
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'>' => array('precedence' => -1),
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'<' => array('precedence' => -1),
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);
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$this->binaryops = array(
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'+', '-', '*', '/', '^', '==', '!=', '<', '<=', '>=', '>',
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);
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$this->funcs = array(
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'ln' => array(
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'function' => 'log',
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'arguments' => 1,
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),
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'arcsin' => array(
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'function' => 'asin',
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'arguments' => 1,
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),
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'arcsinh' => array(
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'function' => 'asinh',
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'arguments' => 1,
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),
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'arccos' => array(
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'function' => 'acos',
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'arguments' => 1,
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),
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'arccosh' => array(
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'function' => 'acosh',
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'arguments' => 1,
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),
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'arctan' => array(
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'function' => 'atan',
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'arguments' => 1,
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),
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'arctanh' => array(
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'function' => 'atanh',
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'arguments' => 1,
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),
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'min' => array(
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'function' => 'min',
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'arguments' => 2,
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'max arguments' => 99,
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),
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'max' => array(
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'function' => 'max',
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'arguments' => 2,
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'max arguments' => 99,
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),
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'pow' => array(
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'function' => 'pow',
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'arguments' => 2,
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),
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'if' => array(
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'function' => 'ctools_math_expr_if',
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'arguments' => 2,
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'max arguments' => 3,
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),
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'number' => array(
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'function' => 'ctools_math_expr_number',
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'arguments' => 1,
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),
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'time' => array(
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'function' => 'time',
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'arguments' => 0,
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),
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);
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// Allow modules to add custom functions.
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$context = array('final' => &$this->funcs);
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drupal_alter('ctools_math_expression_functions', $this->simplefuncs, $context);
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// Set up the initial constants and mark them read-only.
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$this->vars = array('e' => exp(1), 'pi' => pi());
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drupal_alter('ctools_math_expression_constants', $this->vars);
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$this->constvars = array_keys($this->vars);
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// Translate the older, simpler style into the newer, richer style.
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foreach ($this->simplefuncs as $function) {
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$this->funcs[$function] = array(
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'function' => $function,
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'arguments' => 1,
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);
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}
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}
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/**
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* Change the suppress errors flag.
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*
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* When errors are not suppressed, trigger_error is used to cause a PHP error
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* when an evaluation error occurs, as a result of calling trigger(). With
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* errors suppressed this doesn't happen.
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*
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* @param bool $enable
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* If FALSE, enable triggering of php errors when expression errors occurs.
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* otherwise, suppress triggering the errors.
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*
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* @return bool
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* The new (current) state of the flag.
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*
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* @see ctools_math_expr::trigger()
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*/
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public function set_suppress_errors($enable) {
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return $this->suppress_errors = (bool) $enable;
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}
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/**
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* Backwards compatible wrapper for evaluate().
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*
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* @see ctools_math_expr::evaluate()
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*/
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public function e($expr) {
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return $this->evaluate($expr);
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}
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/**
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* Evaluate the expression.
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*
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* @param string $expr
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* The expression to evaluate.
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*
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* @return string|bool
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* The result of the expression, or FALSE if an error occurred, or TRUE if
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* an user-defined function was created.
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*/
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public function evaluate($expr) {
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$this->last_error = NULL;
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$expr = trim($expr);
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// Strip possible semicolons at the end.
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if (substr($expr, -1, 1) == ';') {
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$expr = substr($expr, 0, -1);
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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, $matches)) {
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// Make sure we're not assigning to a constant.
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if (in_array($matches[1], $this->constvars)) {
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return $this->trigger("cannot assign to constant '$matches[1]'");
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}
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// Get the result and make sure it's good:
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if (($tmp = $this->pfx($this->nfx($matches[2]))) === FALSE) {
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return FALSE;
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}
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// If so, stick it in the variable array...
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$this->vars[$matches[1]] = $tmp;
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// ...and return the resulting value:
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return $this->vars[$matches[1]];
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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, $matches)) {
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// Get the function name.
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$fnn = $matches[1];
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// Make sure it isn't built in:
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if (isset($this->funcs[$matches[1]])) {
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return $this->trigger("cannot redefine built-in function '$matches[1]()'");
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}
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// Get the arguments.
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$args = explode(",", preg_replace("/\s+/", "", $matches[2]));
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// See if it can be converted to postfix.
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$stack = $this->nfx($matches[3]);
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if ($stack === FALSE) {
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return FALSE;
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}
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// Freeze the state of the non-argument variables.
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for ($i = 0; $i < count($stack); $i++) {
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$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, $this->vars)) {
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$stack[$i] = $this->vars[$token];
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}
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else {
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return $this->trigger("undefined variable '$token' in function definition");
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}
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}
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}
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$this->userfuncs[$fnn] = array('args' => $args, 'func' => $stack);
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return TRUE;
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}
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else {
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// Straight up evaluation.
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return trim($this->pfx($this->nfx($expr)), '"');
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}
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}
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/**
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* Fetch an array of variables used in the expression.
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*
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* @return array
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* Array of name : value pairs, one for each variable defined.
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*/
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public function vars() {
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$output = $this->vars;
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// @todo: Is this supposed to remove all constants? we should remove all
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// those in $this->constvars!
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unset($output['pi']);
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unset($output['e']);
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return $output;
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}
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/**
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* Fetch all user defined functions in the expression.
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*
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* @return array
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* Array of name : string pairs, one for each function defined. The string
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* will be of the form fname(arg1,arg2). The function body is not returned.
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*/
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public function funcs() {
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$output = array();
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foreach ($this->userfuncs as $fnn => $dat) {
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$output[] = $fnn . '(' . implode(',', $dat['args']) . ')';
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}
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return $output;
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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 $expr
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* The expression to convert.
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*
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* @return array|bool
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* The expression as an ordered list of postfix action tokens.
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*/
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private function nfx($expr) {
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$index = 0;
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$stack = new ctools_math_expr_stack();
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// Postfix form of expression, to be passed to pfx().
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$output = array();
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// @todo: Because the expr can contain string operands, using strtolower here is a bug.
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$expr = trim(strtolower($expr));
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// We use this in syntax-checking the expression and determining when
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// '-' is a negation.
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$expecting_op = FALSE;
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while (TRUE) {
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$op = substr($expr, $index, 1);
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// Get the first character at the current index, and if the second
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// character is an =, add it to our op as well (accounts for <=).
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if (substr($expr, $index + 1, 1) === '=') {
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$op = substr($expr, $index, 2);
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$index++;
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}
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// Find out if we're currently at the beginning of a number/variable/
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// function/parenthesis/operand.
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$ex = preg_match('/^([a-z]\w*\(?|\d+(?:\.\d*)?|\.\d+|\()/', substr($expr, $index), $match);
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// Is it a negation instead of a minus?
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if ($op === '-' and !$expecting_op) {
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// Put a negation on the stack.
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$stack->push('_');
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$index++;
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}
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// We have to explicitly deny this, because it's legal on the stack but
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// not in the input expression.
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elseif ($op == '_') {
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return $this->trigger("illegal character '_'");
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}
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// Are we putting an operator on the stack?
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elseif ((isset($this->ops[$op]) || $ex) && $expecting_op) {
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// Are we expecting an operator but have a num, var, func, or
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// open-paren?
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if ($ex) {
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$op = '*';
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// It's an implicit multiplication.
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$index--;
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}
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// Heart of the algorithm:
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while ($stack->count() > 0 &&
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($o2 = $stack->last()) &&
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isset($this->ops[$o2]) &&
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(!empty($this->ops[$op]['right']) ?
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$this->ops[$op]['precedence'] < $this->ops[$o2]['precedence'] :
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$this->ops[$op]['precedence'] <= $this->ops[$o2]['precedence'])) {
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// Pop stuff off the stack into the output.
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$output[] = $stack->pop();
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}
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// Many thanks: http://en.wikipedia.org/wiki/Reverse_Polish_notation#The_algorithm_in_detail
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// finally put OUR operator onto the stack.
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$stack->push($op);
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$index++;
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$expecting_op = FALSE;
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}
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// Ready to close a parenthesis?
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elseif ($op === ')') {
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// Pop off the stack back to the last '('.
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while (($o2 = $stack->pop()) !== '(') {
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if (is_null($o2)) {
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return $this->trigger("unexpected ')'");
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}
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else {
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$output[] = $o2;
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}
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}
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// Did we just close a function?
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if (preg_match("/^([a-z]\w*)\($/", $stack->last(2), $matches)) {
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// Get the function name.
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$fnn = $matches[1];
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// See how many arguments there were (cleverly stored on the stack,
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// thank you).
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$arg_count = $stack->pop();
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// Pop the function and push onto the output.
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$output[] = $stack->pop();
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// Check the argument count:
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if (isset($this->funcs[$fnn])) {
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$fdef = $this->funcs[$fnn];
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$max_arguments = isset($fdef['max arguments']) ? $fdef['max arguments'] : $fdef['arguments'];
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if ($arg_count > $max_arguments) {
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return $this->trigger("too many arguments ($arg_count given, $max_arguments expected)");
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}
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}
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elseif (array_key_exists($fnn, $this->userfuncs)) {
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$fdef = $this->userfuncs[$fnn];
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if ($arg_count !== count($fdef['args'])) {
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return $this->trigger("wrong number of arguments ($arg_count given, " . count($fdef['args']) . ' expected)');
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}
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}
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else {
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// Did we somehow push a non-function on the stack? this should
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// never happen.
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return $this->trigger('internal error');
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}
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}
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$index++;
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}
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// Did we just finish a function argument?
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elseif ($op === ',' && $expecting_op) {
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$index++;
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$expecting_op = FALSE;
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}
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elseif ($op === '(' && !$expecting_op) {
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$stack->push('(');
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$index++;
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}
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elseif ($ex && !$expecting_op) {
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// Make sure there was a function.
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if (preg_match("/^([a-z]\w*)\($/", $stack->last(3), $matches)) {
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// Pop the argument expression stuff and push onto the output:
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while (($o2 = $stack->pop()) !== '(') {
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// Oops, never had a '('.
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if (is_null($o2)) {
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return $this->trigger("unexpected argument in $expr $o2");
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}
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else {
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$output[] = $o2;
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}
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}
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// Increment the argument count.
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$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;
|
|
}
|