解释器模式

<?php
//解释器模式，把一段有规律的经常用到的内容解释成预期的内容，常用的MVC模式中的模板替换就使用了解释器模式
//一个简单的计算+-*/的计算器，代码比较臃肿。
class Calculator {   
    public function interpreter($str) {
        $str = str_replace(' ', '', $str);
        $str = str_replace(array('+','-','*','/'), array(' + ',' - ',' * ',' / '), $str);
        $arr = explode(' ', $str);
        unset($str);
        $count = count($arr)-1;
        $offset = 1000;
        for($i = 0; $i < $count; ++$i) {
            if ($arr[$i] == '*' || $arr[$i] == '/') {
                $arr[$i-$offset] = $arr[$i];
                if (!isset($arr[$i-1])) {
                    $arr[$i-1] = $tmp;
                }
                $arr[$i-1-$offset] = $arr[$i-1];
                $arr[$i+1-$offset] = $arr[$i+1];
                unset($arr[$i-1]);
                unset($arr[$i]);
                $tmp = $arr[$i+1];
                unset($arr[$i+1]);
                ++$i;
            }
        }
        $left = array();
        $right = array();
        ksort($arr);
        array_walk($arr, function($v, $k) use(&$left, &$right){
            if ($k < 0) {
                $left[]= $v;
            } else {
                $right[]= $v;
            }
        });
        unset($arr);
        $countLeft = count($left) - 1;
        $countRight = count($right) - 1;
        $tmp = array();
        for ($i=0; $i < $countLeft; ++$i) {
            if ($left[$i] == '*' || $left[$i] == '/') {
                if (!isset($left[$i-1])) {
                    $tmpNum = $tmp[count($tmp)-1] = $this->compute($tmpNum, $left[$i+1], $left[$i]);
                    unset($left[$i+1]); 
                } else {
                    $tmpNum = $this->compute($left[$i-1], $left[$i+1], $left[$i]);
                    $tmp[] = $tmpNum;
                    unset($left[$i+1]);
                }
                ++$i;
            }
        }
        unset($left);
        for ($i=0; $i < $countRight; ++$i) {
            if ($right[$i] == '+' || $right[$i] == '-') {
                if ($i == 0) {
                    $input = array(array_shift($tmp));
                    array_splice($right, $i, 0, $input);
                    ++$countRight;
                    continue;
                }
                if ($right[$i+1] == '+' || $right[$i+1] == '-') {
                    $input = array(array_shift($tmp));
                    array_splice($right, $i+1, 0, $input);
                    ++$countRight;
                }
            }
        }
        if (!empty($tmp)) {
            array_push($right, current($tmp));
        }
        $rs = array_shift($right);
        $countRight = count($right);
        for ($i=0; $i < $countRight; ++$i) {
            if ($right[$i] == '+' || $right[$i] == '-') {
                $rs = $this->compute($rs, $right[$i+1], $right[$i]);
            }
        }
        return $rs;
    }

    private function compute($num1, $num2, $expression) {
        switch ($expression) {
            case '+':
                return $num1 + $num2;
            case '-':
                return $num1 - $num2;  
            case '*':
                return $num1 * $num2;
            case '/':
                if ($num2 == 0) {
                    exit('can not divide 0');
                }
                return round($num1 / $num2, 4);
            default:exit('param error');
        }
    }
}

$str = '1-1-2*3*2*3+1+1+2*2*2*2/3-2+3*7*2/2-1+9/3';
$calculator = new Calculator();
$rs = $calculator->interpreter($str);
echo $rs;

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<?php

//解释器模式，把一段有规律的经常用到的内容解释成预期的内容，常用的MVC模式中的模板替换就使用了解释器模式

//一个简单的计算+-*/的计算器，代码比较臃肿。

class Calculator {

public function interpreter($str) {

$str = str_replace(' ', '', $str);

$str = str_replace(array('+','-','*','/'), array(' + ',' - ',' * ',' / '), $str);

$arr = explode(' ', $str);

unset($str);

$count = count($arr)-1;

$offset = 1000;

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

if ($arr[$i] == '*' || $arr[$i] == '/') {

$arr[$i-$offset] = $arr[$i];

if (!isset($arr[$i-1])) {

$arr[$i-1] = $tmp;

}

$arr[$i-1-$offset] = $arr[$i-1];

$arr[$i+1-$offset] = $arr[$i+1];

unset($arr[$i-1]);

unset($arr[$i]);

$tmp = $arr[$i+1];

unset($arr[$i+1]);

++$i;

}

$left = array();

$right = array();

ksort($arr);

array_walk($arr, function($v, $k) use(&$left, &$right){

if ($k < 0) {

$left[]= $v;

} else {

$right[]= $v;

}

});

unset($arr);

$countLeft = count($left) - 1;

$countRight = count($right) - 1;

$tmp = array();

for ($i=0; $i < $countLeft; ++$i) {

if ($left[$i] == '*' || $left[$i] == '/') {

if (!isset($left[$i-1])) {

$tmpNum = $tmp[count($tmp)-1] = $this->compute($tmpNum, $left[$i+1], $left[$i]);

unset($left[$i+1]);

} else {

$tmpNum = $this->compute($left[$i-1], $left[$i+1], $left[$i]);

$tmp[] = $tmpNum;

unset($left[$i+1]);

}

++$i;

}

unset($left);

for ($i=0; $i < $countRight; ++$i) {

if ($right[$i] == '+' || $right[$i] == '-') {

if ($i == 0) {

$input = array(array_shift($tmp));

array_splice($right, $i, 0, $input);

++$countRight;

continue;

}

if ($right[$i+1] == '+' || $right[$i+1] == '-') {

$input = array(array_shift($tmp));

array_splice($right, $i+1, 0, $input);

++$countRight;

}

if (!empty($tmp)) {

array_push($right, current($tmp));

}

$rs = array_shift($right);

$countRight = count($right);

for ($i=0; $i < $countRight; ++$i) {

if ($right[$i] == '+' || $right[$i] == '-') {

$rs = $this->compute($rs, $right[$i+1], $right[$i]);

}

return $rs;

}

private function compute($num1, $num2, $expression) {

switch ($expression) {

case '+':

return $num1 + $num2;

case '-':

return $num1 - $num2;

case '*':

return $num1 * $num2;

case '/':

if ($num2 == 0) {

exit('can not divide 0');

}

return round($num1 / $num2, 4);

default:exit('param error');

}

$str = '1-1-2*3*2*3+1+1+2*2*2*2/3-2+3*7*2/2-1+9/3';

$calculator = new Calculator();

$rs = $calculator->interpreter($str);

echo $rs;

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This is just a personal note.

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