在你看来,你遇到过的最令人惊讶、最怪异、最奇怪或最“WTF”的语言特性是什么?
请每个回答只回答一个特征。
在你看来,你遇到过的最令人惊讶、最怪异、最奇怪或最“WTF”的语言特性是什么?
请每个回答只回答一个特征。
当前回答
在JavaScript中:
2 == [2]
//更陌生 2 == [[[2]]]
//和彻头彻尾的坚果 Var a = {"abc": 1}; A [[[["abc"]]]] === A ["abc"];//这也是正确的
幸运的是,stackoverflow.com网站上善良的人们向我解释了这一切:http:/stackoverflow.com/questions/1724255/why-does-2-2-in-javascript
其他回答
在fortran中(当然是77,可能在95中也是如此),未声明的变量和以I到N开头的参数(“In”组)将是INTEGER,所有其他未声明的变量和参数将是REAL(源)。这与“在某些情况下可选的空白”相结合,导致了最著名的错误之一。
正如弗雷德·韦伯在1990年的《另类民间传说:计算机》一书中所说:
I worked at Nasa during the summer of 1963. The group I was working in was doing preliminary work on the Mission Control Center computer systems and programs. My office mate had the job of testing out an orbit computation program which had been used during the Mercury flights. Running some test data with known answers through it, he was getting answers that were close, but not accurate enough. So, he started looking for numerical problems in the algorithm, checking to make sure his tests data was really correct, etc. After a couple of weeks with no results, he came across a DO statement, in the form: DO 10 I=1.10 This statement was interpreted by the compiler (correctly) as: DO10I = 1.10 The programmer had clearly intended: DO 10 I = 1, 10 After changing the . to a , the program results were correct to the desired accuracy. Apparently, the program's answers had been "good enough" for the sub-orbital Mercury flights, so no one suspected a bug until they tried to get greater accuracy, in anticipation of later orbital and moon flights. As far as I know, this particular bug was never blamed for any actual failure of a space flight, but the other details here seem close enough that I'm sure this incident is the source of the DO story.
我认为这是一个很大的WTF,如果DO10I被作为DO10I,并且反过来,因为隐式声明被认为是类型REAL。这是个很棒的故事。
在Python中,至少对我来说,这是非常wft的!我第一次看的时候:
>>> "ja " * 5
'ja ja ja ja ja '
你可以将字符串相乘!WTF ? ?
PS:我认为这是因为x * n意味着:n乘以x,所以,5次“ja”是“ja”“ja”“ja”“ja”“ja”“ja”,因为你可以像这样连接字符串:
>>> "ja ""ja ""ja ""ja ""ja "
'ja ja ja ja ja '
两个代码有相同的结果(可能是相同的)
Oracle有几个SQL WTF问题。
Oracle将空字符串处理为null。 在“<>”比较中处理空值。 创建表WTF(键数为主键,动物varchar2(10)); 插入WTF值(1,'dog'); Insert into WTF values (2, "); Insert into WTF values (3,'cat'); Select * from WTF where animal <> 'cat';
唯一返回的行是(1,'dog')行。
Algol通过名称传递(使用C语法说明):
int a[3] = { 1, 2, 3 };
int i = 1;
void f(int j)
{
int k;
k = j; // k = 2
i = 0;
k = j; // k = 1 (!?!)
}
int main()
{
f(a[i]);
}
PHP对字符串中数值的处理。详见之前对另一个问题的回答,但简而言之:
"01a4" != "001a4"
如果你有两个包含不同数量字符的字符串,它们不能被认为是相等的。前导零很重要,因为它们是字符串而不是数字。
"01e4" == "001e4"
PHP doesn’t like strings. It’s looking for any excuse it can find to treat your values as numbers. Change the hexadecimal characters in those strings slightly and suddenly PHP decides that these aren’t strings any more, they are numbers in scientific notation (PHP doesn’t care that you used quotes) and they are equivalent because leading zeros are ignored for numbers. To reinforce this point you will find that PHP also evaluates "01e4" == "10000" as true because these are numbers with equivalent values. This is documented behaviour, it’s just not very sensible.