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The UnderflowException class

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

简介

Exception thrown when performing an invalid operation on an empty container, such as removing an element.

类摘要

class UnderflowException extends RuntimeException {

/* 继承的属性 */

protected string $message = "";

private string $string = "";

protected int $code;

protected string $file = "";

protected int $line;

private array $trace = [];

private ?Throwable $previous = null;

/* 继承的方法 */

public Exception::__construct(string $message = "", int $code = 0, ?Throwable $previous = null)

final public Exception::getMessage(): string

final public Exception::getPrevious(): ?Throwable

final public Exception::getCode(): int

final public Exception::getFile(): string

final public Exception::getLine(): int

final public Exception::getTrace(): array

final public Exception::getTraceAsString(): string

public Exception::__toString(): string

private Exception::__clone(): void

}

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User Contributed Notes 2 notes

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Jakub Adamczyk ¶

1 year ago

The most typical usage is with stack, queue or collection, for example when you queue tasks, make call stack or manipulate JSON, XML, etc. elements.

As other exepctions of RuntimeException class, this type of error can't be detected in (for example) your IDE or compiler.

<?php
// Functions declared above 
$f1 = function() { setTypeControl('username');};
$f2 = function() { setTypeControl('userpass');};
$f3 = function() { setButton('Add');};
$f4 = function() { setButton('OK');};

$tasks = new class {
    private $list;

    // Create internal queue
    public function __construct() {
        $this->list = new SplQueue;
    }

    // Add to queue
    public function add(callable $func) {
        $this->list->enqueue($func);
    }

    // Delete from queue and execute
    public function do() {
        if ($this->list->isEmpty()) {
            throw new UnderflowException;
        } else {
            call_user_func($this->list->dequeue());
        }
    }

};

$tasks->add($f1);
$tasks->add($f2);
$tasks->add($f3);
$tasks->add($f4);

$tasks->do(); // Field username is created
$tasks->do(); // Field userpass is created
$tasks->do(); // Button Add is created
$tasks->do(); // Button OK is created
$tasks->do(); // Fatal error: Uncaught UnderflowException in ...

down

-9

evguenia dot chagnon at gmail dot com ¶

6 years ago

UnderflowException handles exceptions due to a value being too small to maintain precision, resulting in loss of accuracy. In PHP, this can occurs when using floats:

echo (1-0.9) // 0.1
echo (1-0.99) // 0.01
echo (1-0.999) // 0.001
echo (1-0.9999) // 9.9999999999989E-05
echo (1-0.99999) // 9.9999999999545E-06
echo (1-0.999999) // 1.0000000000288E-06

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