Question

InputForm[{a, b, c, d, e, f}]提供{a, b, c, d, e, f}

InputForm[Characters["SOMETHING"]]提供{"S", "O", "M", "E", "T", "H", "I", "N", "G"}

但为什么Drop[InputForm[Characters["SOMETHING"]],1]不给{"O", "M", "E", "T", "H", "I", "N", "G"}

但是给出了一个InputForm []而没有别的？

我怎样才能做到这一点？

谢谢

Answer 1

评估时

InputForm[Characters["SOMETHING"]]

Mathematica在内部产生结果

InputForm[List["S","O","M","E","T","H","I","N","G"]]

即。它是以InputForm为首的表达式，其中包含ListList["S","O","M","E","T","H","I","N","G"]作为其第一个子表达式。当Mathematica显示表达式时，您不会看到InputForm头部，因为前端仅使用它作为如何显示表达式的提示，但它仍然存在于幕后

然后当你使用Drop[..., 1]时，它会查看它给出的表达式，选出第一个子表达式，即List["S","O","M","E","T","H","I","N","G"]，并将其丢弃。这只留下InputForm[]。

进行类比：如果你评估了

Drop[List[List["S","O","M","E","T","H","I","N","G"]], 1]

你会理解为什么你会得到一个空列表，对吧？发生了同样的事情。

字符串操作中的混乱

1 个答案: