logical-operators | 易学教程

Compound relational operators in C

阅读更多关于 Compound relational operators in C

问题 I am trying to convert a piece of pseudo code into a C code and I have conditions like if (-4 <= X <=8) THEN {Do Something} else {Do something else} Is the syntax in if statement valid? Can a constant be placed before the variable in the logical condition to check the truth value? 回答1: Yes you can have constants as the left hand argument of a logical check in C. However the pseudocode you have listed would need to be split into two expressions: if ((-1 <= X) && (X <= 8)) Side Note: Many

Logical short-circuit inside a function handle

阅读更多关于 Logical short-circuit inside a function handle

问题 I have a function handle that operates on 2d arrays of arbitrary size: R2T = @(DL1,DL2) arrayfun(@(DL1,DL2)... 1/(fzero(@(x)fFitObj1(x)./fFitObj2(x)-... DL1./DL2,[minLim maxLim])) ... ,DL1,DL2) - C1; Here's a bottom-up breakdown of what it does: fzero(@(x)fFitObj1(x)./fFitObj2(x)-DL1./DL2,[minLim maxLim]) - This bit looks for a zero of the considered function on the interval [minLim maxLim] , where fFitObj1 and fFitObj2 are function handles available from before, C1 is some known constant and

C# - | and & operators?

阅读更多关于 C# - | and & operators?

问题 edit: My main question now is why these two operators need to be overloaded to use the && and || operators. Wouldn't the short-circuit operators take the true or false values of the objects and compare those? Where in the use of the && and || operators is | and & used? I'm reading C#, the complete reference, and I'm quite confused about the | and & operators. I'm used to them being bitwise operators that compare the bits of two integers, but they're explained as the original logical operators

Pandas Equivalent of R's which()

阅读更多关于 Pandas Equivalent of R's which()

Variations of this question have been asked before, I'm still having trouble understanding how to actually slice a python series/pandas dataframe based on conditions that I'd like to set. In R, what I'm trying to do is: df[which(df[,colnumber] > somenumberIchoose),] The which() function finds indices of row entries in a column in the dataframe which are greater than somenumberIchoose, and returns this as a vector. Then, I slice the dataframe by using these row indices to indicate which rows of the dataframe I would like to look at in the new form. Is there an equivalent way to do this in

Confused by use of double logical not (!!) operator [duplicate]

阅读更多关于 Confused by use of double logical not (!!) operator [duplicate]

This question already has an answer here: Double Negation in C++ code 14 answers What is “!!” in C? [duplicate] 7 answers I have some C++ code that makes extensive use of !! . I'm kinda baffled because as far as I know !! is not a operator on it's own but two ! after each other. So that would mean that !!foo is the same as just foo . Is there any place and or reason when !! actually makes sense? I was thinking about if it could perhaps have a bit wise meaning? So you first perform some bit wise operation on foo and then ! on the result? But I don't seem to remember ! being used as a bit wise

Behaviour of && in C programming language

阅读更多关于 Behaviour of && in C programming language

问题 I am beginner in C programming language, recently I have read about Logical AND && operator. I also know that, in C programming language all non-zero values are treated as TRUE . NON-ZERO && NON-ZERO = 1 NON-ZERO && ZERO = 0 ZERO && NON-ZERO = 0 ZERO && ZERO = 0 But when I am dealing with the following program then I am not getting expected answer. int main(){ int x, y, z; x = y = z = -1; y = ++x && ++y && ++z; printf("x = %d, y = %d, z = %d, x, y, z); return 0; } I am expecting x = 0, y = 0,

How do I use the bitwise operator XOR in Lua?

阅读更多关于 How do I use the bitwise operator XOR in Lua?

How can I implement bitwise operators in Lua language? Specifically, I need a XOR operator/method. Yu Hao In Lua 5.2, you can use functions in bit32 library. In Lua 5.3, bit32 library is obsoleted because there are now native bitwise operators . print(3 & 5) -- bitwise and print(3 | 5) -- bitwise or print(3 ~ 5) -- bitwise xor print(7 >> 1) -- bitwise right shift print(7 << 1) -- bitwise left shift print(~7) -- bitwise not Output: 1 7 6 3 14 -8 In Lua 5.2, you can use the bit32.bxor function. Since you're referencing the floor function 3 times, using an excessive number of loops for most

Operands to the || and && operators must be convertible to logical scalar values

阅读更多关于 Operands to the || and && operators must be convertible to logical scalar values

问题 I have a simple problem that I'm looking for a fast implementation in Matlab. I have an array of values, let's say: a = floor(rand(5,5).*255) I then have a similarly sized threshold array, let's say it's: a_thresh = floor(rand(5,5).*255) For values within a if they are 0.5x smaller than the corresponding value in a_thresh I want the output to be 0 - similarly for 1.2x the value in a_thresh should also be set to zero, i.e. : a(a < a_thresh.*0.4) = 0 a(a > a_thresh.*1.2) = 0 For values between

What's the difference between “<>” and “!=”? [duplicate]

阅读更多关于 What's the difference between “” and “!=”? [duplicate]

问题 This question already has answers here : Difference between “not equal” operators <> and != in PHP (6 answers) Closed 5 years ago . Normally I would use != , then when I saw this sign <> it means not equal to as well. After that, I went to search on Google, what's the difference between <> and != . But I could not find the answer. Anyone care to explain? 回答1: <> has a higher precedence than != . Otherwise they're identical. 回答2: There is no difference. Some languages use <> and some use !=,

Is there a difference between using a logical operator or a bitwise operator in an if block in Java?

阅读更多关于 Is there a difference between using a logical operator or a bitwise operator in an if block in Java?

The contents of both of the following if blocks should be executed: if( booleanFunction() || otherBooleanFunction() ) {...} if( booleanFunction() | otherBooleanFunction() ) {...} So what's the difference between using | or using || ? Note: I looked into this and found my own answer, which I included below. Please feel free to correct me or give your own view. There sure is room for improvement! The two have different uses. Although in many cases (when dealing with booleans) it may appear that they have the same effect, it is important to note that the logical-OR is short circuit, meaning that