签署无签名和副Versa（算术） [英] Signed to Unsigned and Vice Versa (arithmetical)

问题描述

如何将数字从无符号转换为有符号？

How to convert a number from unsigned to signed?

已签名：-32768至32767
无符号：0至65535

signed: -32768 to 32767 unsigned: 0 to 65535

我正在解决JavaScript中的问题。情况是，我有一个例如从0到65535，我想将其转换为合理的有符号值。

I am solving the problem in JavaScript. The situation is that I have a number that goes e.g. from 0 to 65535 and I want to convert it to a reasonable signed value.

例如：65535应该变为-1。

e.g.: 65535 should become -1.

请不要使用任何与位相关的操作，而是使用算术。

Please do not use any bit related operations but something arithmetical.

我想这应该是语言无关的，假设我们使用的数据类型足够大。

I guess this should be language independent assuming that we use a data type that is big enough.

更新：
根据答案进一步实施：

Update: Implementation according to the answer further down:

function convertWordToShort(ival) {
    if (isNaN(ival) === false) {
        if (ival > 32767) {
            ival = ival - 65536;
        }
    }
    return ival;
}
function convertShortToWord(ival) {
    if (isNaN(ival) === false) {
        if (ival < 0) {
            ival = ival + 65536;
        }
    }
    return ival;
}
function convertIntToDWord(ival) {
    if (isNaN(ival) === false) {
        if (ival < 0) {
            ival = ival + 4294967296;
        }
    }
    return ival;
}
function convertDWordToInt(ival) {
    if (isNaN(ival) === false) {
        if (ival > 2147483647) {
            ival = ival - 4294967296;
        }
    }
    return ival;
}

推荐答案

只测试数字是否为超过一半，然后减去模数。

Just test if the number is over halfway, then subtract the modulus.

if(x > 32767) {x = x - 65536;}

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