1:  2:  3:  4:  5:  6:  7:  8:  9: 10: 11: 12: 13: 14: 15: 16: 17: 18: 19: 20: 21: 22: 23: 24: 25: 26: 27: 28: 29: 30: 31: 32: 33: 34: 35: 36: 37: 38: 39: 40: 41: 42: 43: 44: 45: 46: 47: 48: 49: 50: 51: 52: 53: 54: 55: 56: 57: 58: 59: 60: 61: 62: 63: 64: 65: 66: 67: 68: 69: 70: 71: 

<?php
/*
 * Math-Matrix library
 *
 * @author Ashley Kitson <akitson@zf4.biz>
 * @copyright Ashley Kitson, UK, 2014
 * @licence GPL V3 or later : http://www.gnu.org/licenses/gpl.html
 * @link http://en.wikipedia.org/wiki/Matrix_(mathematics)
 */
namespace Chippyash\Math\Matrix\Attribute;

use Chippyash\Matrix\Interfaces\AttributeInterface;
use Chippyash\Matrix\Matrix;
use Chippyash\Math\Matrix\NumericMatrix;
use Chippyash\Type\Interfaces\NumericTypeInterface;
use Chippyash\Type\Number\Complex\ComplexType;

/**
 * Is matrix an identity matrix?
 * Can only be applied to numeric and complex matrices
 */
class IsIdentity implements AttributeInterface
{

    /**
     * Does the matrix have this attribute
     * @link http://en.wikipedia.org/wiki/Identity_matrix
     *
     * @param Matrix $mA
     * @return boolean
     */
    public function is(Matrix $mA)
    {
        if (!$mA instanceof NumericMatrix) {
            return false;
        }
        $rows = $mA->rows();
        $cols = $mA->columns();
        $data = $mA->toArray();
        for ($r = 0; $r < $rows; $r++) {
            for ($c = 0; $c < $cols; $c++) {
                $item = $this->checkItem($data[$r][$c]);
                //diagonal == 1
                if (($r == $c) && $item != 1) {
                    return false;
                //non-diagonal == 0
                } elseif (($r != $c) && $item != 0) {
                    return false;
                }
            }
        }

        return true;
    }

    protected function checkItem($item)
    {
        if ($item instanceof ComplexType) {
            if ($item() == '1+0i') {
                return 1;
            } elseif ($item->isZero()) {
                return 0;
            } else {
                return -1;
            }
        }
        //any other numericType will caste down as required
        return $item();
    }
}