boolean-operations

Why doesn't c++ have &&= or ||= for booleans?

由 落爺英雄遲暮 提交于 2019-11-27 04:14:42
问题 Is there a "very bad thing" that can happen &&= and ||= were used as syntactic sugar for bool foo = foo && bar and bool foo = foo || bar ? 回答1: A bool may only be true or false in C++. As such, using &= and |= is relatively safe (even though I don’t particularly like the notation). True, they will perform bit operations rather than logical operations (and thus they won’t short-circuit) but these bit operations follow a well-defined mapping, which is effectively equivalent to the logical

Why do most programming languages only have binary equality comparison operators?

由 别来无恙 提交于 2019-11-27 01:16:19
问题 In natural languages, we would say "some color is a primary color if the color is red, blue, or yellow." In every programming language I've seen, that translates into something like: isPrimaryColor = someColor == "Red" or someColor == "Blue" or someColor == "Yellow" Why isn't there a syntax that more closely matches the English sentence. After all, you wouldn't say "some color is a primary color if that color is red, or that color is blue, or that color is yellow." I realize simply

String compare on a bool

由 廉价感情. 提交于 2019-11-26 22:00:59
问题 I'm pretty sure this is a simple fundamental flaw in my newb PHP knowledge, but I was surprised when the following happened: $result is TRUE ... so why is it considered equal to the string "email"? I'm guessing this is because, technically, it's a bool and it isn't false? So when it's compared against a string (e.g. "email") it returns true. Should I change my method to return as the result as a string containing "true" (instead of return true; on success), or is there another way I should be

Using “and” and “or” operator with Python strings [duplicate]

由 我与影子孤独终老i 提交于 2019-11-26 20:42:30
This question already has an answer here: Strange use of “and” / “or” operator 8 answers I don't understand the meaning of the line: parameter and (" " + parameter) or "" where parameter is string Why would one want to use and and or operator, in general, with python strings? Suppose you are using the value of parameter , but if the value is say None , then you would rather like to have an empty string "" instead of None . What would you do in general? if parameter: # use parameter (well your expression using `" " + parameter` in this case else: # use "" This is what that expression is doing.

How to calculate boolean expression in Spirit

由 て烟熏妆下的殇ゞ 提交于 2019-11-26 18:25:09
问题 I found a really good example about boolean translator, * Boolean expression (grammar) parser in c++ What I am thinking now is to do a further step, translate (!T|F)&T into F or 0 , so it is very convenient for calculating a very long boolean expression. Is there some examples about this using spirit? What I have done is making a calculator first, and then let it calculate '(T+!F*T)', which equal to (T||!F&&T) but when I type () , there is an error. How to modify it? Thanks a lot! #include

Element-wise logical OR in Pandas

由 核能气质少年 提交于 2019-11-26 12:28:47
问题 I would like the element-wise logical OR operator. I know \"or\" itself is not what I am looking for. I am aware that AND corresponds to & and NOT, ~ . But what about OR? 回答1: The corresponding operator is | : df[(df < 3) | (df == 5)] would elementwise check if value is less than 3 or equal to 5. If you need a function to do this, we have np.logical_or. For two conditions, you can use df[np.logical_or(df<3, df==5)] Or, for multiple conditions use the logical_or.reduce , df[np.logical_or

deMorgan rules explained

由 六月ゝ 毕业季﹏ 提交于 2019-11-26 09:37:20
问题 Could you please explain the deMorgan rules as simply as possible (e.g. to someone with only a secondary school mathematics background) ? 回答1: We have two values: T and F . We can combine these values in three ways: NOT , AND , and OR . NOT is the simplest: NOT T = F NOT F = T We can write this as a truth table : when given.. | results in... ============================ T | F F | T For conciseness x | NOT x ========= T | F F | T Think of NOT as the complement , that is, it turns one value

Using “and” and “or” operator with Python strings [duplicate]

由 断了今生、忘了曾经 提交于 2019-11-26 07:41:02
问题 This question already has answers here : How do “and” and “or” act with non-boolean values? (8 answers) Closed 11 months ago . I don\'t understand the meaning of the line: parameter and (\" \" + parameter) or \"\" where parameter is string Why would one want to use and and or operator, in general, with python strings? 回答1: Suppose you are using the value of parameter , but if the value is say None , then you would rather like to have an empty string "" instead of None . What would you do in

Boolean operators vs Bitwise operators

由 倖福魔咒の 提交于 2019-11-25 23:18:41
问题 I am confused as to when I should use Boolean vs bitwise operators and vs & or vs | Could someone enlighten me as to when do i use each and when will using one over the other affect my results? 回答1: Here are a couple of guidelines: Boolean operators are usually used on boolean values but bitwise operators are usually used on integer values. Boolean operators are short-circuiting but bitwise operators are not short-circuiting. The short-circuiting behaviour is useful in expressions like this:

Boolean operators && and ||

由 大兔子大兔子 提交于 2019-11-25 22:26:18
问题 According to the R language definition, the difference between & and && (correspondingly | and || ) is that the former is vectorized while the latter is not. According to the help text, I read the difference akin to the difference between an \"And\" and \"AndAlso\" (correspondingly \"Or\" and \"OrElse\")... Meaning: That not all evaluations if they don\'t have to be (i.e. A or B or C is always true if A is true, so stop evaluating if A is true) Could someone shed light here? Also, is there an
订阅 boolean-operations