php計算器類

Question

我被困在解決PHP腳本。

我想計算一組指令的結果。說明由每行空格分隔的關鍵字和數字組成。指令從文件加載並將結果輸出到屏幕。可以指定任意數量的指令。指令是操作符（添加，除，減，乘）。說明將忽略數學優先級。最後一條指令應該是「apply」和一個數字（例如「apply 3」）。計算器隨後用該號碼初始化，並將前面的指令應用於該號碼。

[Input] 
add 2 
multiply 3 
apply 3 
[Output] 
15 

這是我已經試過，但我不能讓邏輯來完成方法

class Calculator { 
    public $result = 0; 
    public $queue = Array(); 
    public parseString($text) { 
     // parse input string 
     $cmds = explode(" ", $text); 
     foreach($cmds as $cmd) { 
      $cmd = trim($cmd); 
      if(!$cmd) continue; // blank or space, ignoring 
      $this->queue[] = $cmd; 
     } 

     // lets process commands 
     $command = false; 
     foreach($this->queue as $index => $cmd) { 
      if(is_number($cmd)) { 
       // if it's number fire previous command if exists 
       if(!$command || !method_exists($this, $command)) { 
        throw new Exception("Unknown command $command"); 
       } 
       $this->$command($index, $cmd); 
      }else{ 
       $command = $cmd; 
      } 
     } 
    } 
    public function apply($index, $number) { 
     // manipulate $result, $queue, $number 
    } 
    public function add($index, $number) { 
     // manipulate $result, $queue, $number 
    } 
    public function substract($index, $number) { 
     // manipulate $result, $queue, $number 
    } 
} 

$calculator = new Calculator(); 
$calculator->parseString('...'); 

我怎麼能叫或切換加，除，乘。減去和如何區分和觸發申請word

任何形式的幫助將不勝感激。

Answer 1

您應該處理的申請，然後再剪下來的隊列排列的。在開始循環執行命令之前，只需測試apply命令並首先運行它。這簡化了整個過程。

實驗和聊天多分鐘後，已經解決了。

<?php 
error_reporting(E_ALL); 
class Calculator { 

public $result = 0; 
public $queue = array(); 

public function parseString($text) { 

    // parse input string 
    $split = explode(" ", $text); //This gets your input into new lines 
    for ($i = 0; $i < count($split); $i += 2) $pairs[] = array($split[$i], $split[$i+1]); 

    foreach ($pairs as $bits) { 
     if ($bits[0] == "apply") { 
      $this->apply($bits[1]); //Set result equal to apply. 
      $this->queue[] = "output"; 
     } else { 
      $this->queue[] = $bits; //Set the queue item as an array of (command, value). 
     } 
    } 
    //var_dump($this->queue); 
    //die; 
    // lets process commands 
    foreach ($this->queue as $index => $cmd) { 
     if ($cmd == "output") { 
      echo "Answer: " .$this->result; 
      return; 
     } else { 
      switch($cmd[0]) { 
       case "add": 
        $this->add($cmd[1]); 
        break; 
       case "subtract": 
        $this->subtract($cmd[1]); 
        break; 
       case "multiply": 
        $this->multiply($cmd[1]); 
        break; 
       case "divide": 
        $this->divide($cmd[1]); 
        break; 
       default: 
        echo "Unknown command!"; 
        break; 
      } 
     } 
    } 
} 

public function apply($number) { 
    // manipulate $result, $queue, $number 
    $this->result = $number; 

} 

public function add($number) { 
    // manipulate $result, $queue, $number 
    $this->result += $number; 

} 

public function subtract($number) { 
    // manipulate $result, $queue, $number 
    $this->result -= $number; 

} 

public function multiply($number) { 
    // manipulate $result, $queue, $number 
    $this->result *= $number; 
} 

public function divide($number) { 
    // manipulate $result, $queue, $number 
    $this->result /= $number; 
} 

} 
?> 

Answer 2

嘗試使用array_shift and array_pop功能：

//pop the apply num off end off the queue 
$result= array_pop($this->queue); 
//now pop the apply operator off end of the queue 
$operator = array_pop($this->queue); 

//now get the first operator and numbers using array_shift 
$operator = array_shift($this->queue); //get first operator 
$num = array_shift($this->queue); //get first number 

//loop perform operation on result using number till done. 
while($num !== null) 
{ 
    $result = $operator($result, $num); 
    $operator = array_shift($this->queue); 
    $num = array_shift($this->queue); 
}