class.ilMath.php

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<?php
/*
        +-----------------------------------------------------------------------------+
        | ILIAS open source                                                           |
        +-----------------------------------------------------------------------------+
        | Copyright (c) 1998-2006 ILIAS open source, University of Cologne            |
        |                                                                             |
        | This program is free software; you can redistribute it and/or               |
        | modify it under the terms of the GNU General Public License                 |
        | as published by the Free Software Foundation; either version 2              |
        | of the License, or (at your option) any later version.                      |
        |                                                                             |
        | This program is distributed in the hope that it will be useful,             |
        | but WITHOUT ANY WARRANTY; without even the implied warranty of              |
        | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               |
        | GNU General Public License for more details.                                |
        |                                                                             |
        | You should have received a copy of the GNU General Public License           |
        | along with this program; if not, write to the Free Software                 |
        | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. |
        +-----------------------------------------------------------------------------+
*/

class ilMath
{
        /*
        * Add two numbers
        */
        public static function _add($left_operand, $right_operand, $scale = 50)
        {
                $left_operand=ilMath::bcconv($left_operand);
                $right_operand=ilMath::bcconv($right_operand);
                $scale=ilMath::bcconv($scale);
                
                if (function_exists("bcadd"))
                {
                        return bcadd($left_operand, $right_operand, $scale);
                }
                else
                {
                        $res = $left_operand + $right_operand;
                        if (is_numeric($scale)) $res = round($res, $scale);
                        return $res;
                }
        }

        /*
        * Compare two numbers
        */
        public static function _comp($left_operand, $right_operand, $scale = 50)
        {
                $left_operand=ilMath::bcconv($left_operand);
                $right_operand=ilMath::bcconv($right_operand);
                $scale=ilMath::bcconv($scale);
                
                if (function_exists("bccomp"))
                {
                        return bccomp($left_operand, $right_operand, $scale);
                }
                else
                {
                        if (is_numeric($scale)) 
                        {
                                $left_operand = round($left_operand, $scale);
                                $right_operand = round($right_operand, $scale);
                        }
                        if ($left_operand == $right_operand) return 0;
                        if ($left_operand > $right_operand) return 1;
                        return -1;
                }
        }

        /*
        * Divide two numbers
        */
        public static function _div($left_operand, $right_operand, $scale = 50)
        {
                $left_operand=ilMath::bcconv($left_operand);
                $right_operand=ilMath::bcconv($right_operand);
                $scale=ilMath::bcconv($scale);
                
                if (function_exists("bcdiv"))
                {
                        return bcdiv($left_operand, $right_operand, $scale);
                }
                else
                {
                        if ($right_operand == 0) return NULL;
                        $res = $left_operand / $right_operand;
                        if (is_numeric($scale)) $res = round($res, $scale);
                        return $res;
                }
        }

        /*
        * Get modulus of two numbers
        */
        public static function _mod($left_operand, $modulus)
        {
                $left_operand=ilMath::bcconv($left_operand);
                $modulus=ilMath::bcconv($modulus);
                
                if (function_exists("bcmod"))
                {
                        return bcmod($left_operand, $modulus);
                }
                else
                {
                        return $left_operand % $modulus;
                }
        }

        /*
        * Multiplicate two numbers
        */
        public static function _mul($left_operand, $right_operand, $scale = 50)
        {
                $left_operand=ilMath::bcconv($left_operand);
                $right_operand=ilMath::bcconv($right_operand);
                $scale=ilMath::bcconv($scale);
                
                if (function_exists("bcmul"))
                {
                        return bcmul($left_operand, $right_operand, $scale);
                }
                else
                {
                        $res = $left_operand * $right_operand;
                        if (is_numeric($scale)) $res = round($res, $scale);
                        return $res;
                }
        }

        /*
        * Raise a number to another
        */
        public static function _pow($left_operand, $right_operand, $scale = 50)
        {
                $left_operand=ilMath::bcconv($left_operand);
                $right_operand=ilMath::bcconv($right_operand);
                $scale=ilMath::bcconv($scale);
                
                if(function_exists("bcpow"))
                {
                        // bcpow() only supports exponents less than or equal to 2^31-1.
                        // Also, bcpow() does not support decimal numbers.
                        // If you have scale set to 0, then the exponent is converted to an integer; otherwise an error is generated.
                        $left_operand_dec  = ilMath::exp2dec($left_operand);
                        $right_operand_dec = ilMath::exp2dec($right_operand);

                        $is_exponent_decimal_number = strpos($right_operand_dec, '.') !== false;

                        // bcpow does NOT support decimal exponents
                        if(!$is_exponent_decimal_number)
                        {
                                return bcpow($left_operand_dec, $right_operand_dec, $scale);
                        }
                }
                
                $res = pow($left_operand, $right_operand);
                if (is_numeric($scale)) $res = round($res, $scale);
                return $res;
        }

        /*
        * Get the square root of a number
        */
        public static function _sqrt($operand, $scale = 50)
        {
                $operand=ilMath::bcconv($operand);
                $scale=ilMath::bcconv($scale);
                
                if (function_exists("bcsqrt"))
                {
                        return bcsqrt($operand, $scale);
                }
                else
                {
                        $res = sqrt($operand);
                        if (is_numeric($scale)) $res = round($res, $scale);
                        return $res;
                }
        }

        /*
        * Subtract two numbers
        */
        public static function _sub($left_operand, $right_operand, $scale = 50)
        {
                $left_operand=ilMath::bcconv($left_operand);
                $right_operand=ilMath::bcconv($right_operand);
                $scale=ilMath::bcconv($scale);
                
                if (function_exists("bcsub"))
                {
                        return bcsub($left_operand, $right_operand, $scale);
                }
                else
                {
                        $res = $left_operand - $right_operand;
                        if (is_numeric($scale)) $res = round($res, $scale);
                        return $res;
                }
        }

        /*
        * Converts numbers in the form "1.5e4" into decimal notation
        * Only available for bcmath
        */
        function exp2dec($float_str)
        {
                // make sure its a standard php float string (i.e. change 0.2e+2 to 20)
                // php will automatically format floats decimally if they are within a certain range
                $original = $float_str; // store original float, so we can return a float keeping the pecision when possible
                $float_str = (string)((float)($float_str));
                $float_str = str_replace(",", ".", $float_str); // convert ',' to '.' (float casting was locale sensitive)

                // if there is an E in the float string
                if(($pos = strpos(strtolower($float_str), 'e')) !== false)
                {
                        // get either side of the E, e.g. 1.6E+6 => exp E+6, num 1.6
                        $exp = substr($float_str, $pos+1);
                        $num = substr($float_str, 0, $pos);

                        // strip off num sign, if there is one, and leave it off if its + (not required)
                        if((($num_sign = $num[0]) === '+') || ($num_sign === '-')) $num = substr($num, 1);
                        else $num_sign = '';
                        if($num_sign === '+') $num_sign = '';

                        // strip off exponential sign ('+' or '-' as in 'E+6') if there is one, otherwise throw error, e.g. E+6 => '+'
                        if((($exp_sign = $exp[0]) === '+') || ($exp_sign === '-')) $exp = substr($exp, 1);
                        else trigger_error("Could not convert exponential notation to decimal notation: invalid float string '$float_str'", E_USER_ERROR);

                        // get the number of decimal places to the right of the decimal point (or 0 if there is no dec point), e.g., 1.6 => 1
                        $right_dec_places = (($dec_pos = strpos($num, '.')) === false) ? 0 : strlen(substr($num, $dec_pos+1));
                        // get the number of decimal places to the left of the decimal point (or the length of the entire num if there is no dec point), e.g. 1.6 => 1
                        $left_dec_places = ($dec_pos === false) ? strlen($num) : strlen(substr($num, 0, $dec_pos));

                        // work out number of zeros from exp, exp sign and dec places, e.g. exp 6, exp sign +, dec places 1 => num zeros 5
                        if($exp_sign === '+') $num_zeros = $exp - $right_dec_places;
                        else $num_zeros = $exp - $left_dec_places;

                        // build a string with $num_zeros zeros, e.g. '0' 5 times => '00000'
                        $zeros = str_pad('', $num_zeros, '0');

                        // strip decimal from num, e.g. 1.6 => 16
                        if($dec_pos !== false) $num = str_replace('.', '', $num);

                        // if positive exponent, return like 1600000
                        if($exp_sign === '+') return $num_sign.$num.$zeros;
                        // if negative exponent, return like 0.0000016
                        else return $num_sign.'0.'.$zeros.$num;
                }
                // otherwise, assume already in decimal notation and return
                else return $original;
        }
                    
        public static function isCoprimeFraction($numerator, $denominator)
        {
                $gcd = self::getGreatestCommonDivisor(abs($numerator), abs($denominator));

                return $gcd == 1 ? true : false;
        }

        public static function getGreatestCommonDivisor($a, $b)
        {
                if ($b > 0)
                {
                        return self::getGreatestCommonDivisor($b, $a % $b);
                }
                else
                {
                        return $a;
                }
        }

        public static function _round($value, $precision = 0)
        {
                return number_format($value, $precision, '.', '');
        }
        
        public static function _equals($value1, $value2, $scale)
        {
                return self::_comp($value1, $value2, $scale) === 0;
        }

        private static function bcconv($fNumber)
        {
                $fNumber=ilMath::exp2dec($fNumber);
                $locale_info = localeconv();
                if($locale_info["decimal_point"] != ".")
                {
                        $sAppend = '';
                        $iDecimals = ini_get('precision') - floor(log10(abs($fNumber)));
                        if (0 > $iDecimals)
                        {
                                $fNumber *= pow(10, $iDecimals);
                                $sAppend = str_repeat('0', -$iDecimals);
                                $iDecimals = 0;
                        }
                        return number_format($fNumber, $iDecimals, '.', '').$sAppend;
                }
                return $fNumber;
        }
}
?>