两个减号在一起的含义(“双一元") [英] Meaning of two minus signs together ("double unary")

问题描述

公式开头的两个 - 符号是什么意思?

What does the two - sign mean at the beginning of a formula?

例如:此公式获取字符串日期并将其转换为 Excel 日期序列号:

Ex: This formula gets a string date and converts it into an Excel date serial number:

=--(MID(S2,4,3)&LEFT(S2,3)&MID(S2,7,4))

公式没问题，我只是想了解公式中的--

The formula works fine, I just want to understand the -- in the formula.

推荐答案

@JNevill 的评论对我来说似乎是一个很好的答案，但为了得到答案，请考虑 A1 和 Y<中的 Y/code> 在 B1 中.这个公式:

@JNevill's Comment seems a good answer to me but for the sake of an Answer consider Y in A1 and Y in B1. This formula:

=(A1=B1)  

返回 TRUE.如前所述，在前面贴上一个运算符(带有0+，或1*)，布尔值就变成了1，或0 如果 B1(仅)更改为 X.

returns TRUE. As mentioned, stick an operator in front (with 0+, or 1*) and the Boolean is turned into 1, or 0 if B1 (only) is changed to, say, X.

单个减号否定了这一点.0-，或-1*，在前面返回-1对于A1和B1都等于Y.否定 that 并且 -1 结果变成 1，用 =--1*(A1=B1) 说.

The single minus negates that. 0-, or -1*, at the front returns -1 for both A1 and B1 equal to Y. Negate that and the -1 result becomes 1, say with =--1*(A1=B1).

但是乘以一(或加零)是没有意义的，不妨直接去做:

But then multiplying by one (or adding zero) is pointless, might as well just go for:

=--(A1=B1)  

请注意，由于评估发生的顺序，以上与以下不同:

Note that because of the order in which the evaluations take place, the above is not the same as:

=--A1=B1  

没有意义所以返回#VALUE!.

文本函数(在您的示例中为 MID 和 LEFT)返回字符串，因此例如使用此类函数构建今天的日期索引(1900 年日期系统中的 42311)(单独)返回五个 Excel 无法识别为可能代表日期的字符.转换为数字格式并表示为日期，这应该看起来像今天".

Text functions (MID and LEFT in your example) return strings, so constructing a date index for today for example (42311 in the 1900 date system) with such functions (alone) returns five characters Excel does not recognise as possibly representing a date. Converted to numeric format and represented as a date this should look like 'today'.

因此将单元格格式化为Text并输入42311，然后重新格式化为Date，结果仍然是42311.将单元格格式化为常规并输入:

So format a cell as Text and enter 42311, then reformat as Date and the result is still 42311. Format a cell as General and enter:

=--("42"&"311")

在格式化为日期之前，您应该会看到类似今天"的内容.

before then formatting as Date and you should see something that looks like 'today'.

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