logical-operators

问题 I have the following table (5 columns and 3 rows) called mat : AC CA RES 1 0 2 2 1 3 0 0 0 1 The operation being performed is mat[1]/mat[1]+mat[2] I am testing for the following : 1) If both columns of a row are zero, the result should be NA. 2) If only one column of a row is zero and the other has a non-zero number, proceed with calculation. (Even if the numerator is 0, that's okay) I am currently using this if-else structure within a for-loop going row-wise: if(mat[b,1]>=0|mat[b,2]>=0){mat

问题 I am using Intel Fortran in Visual Studio 2012 to compile a Fortran code. When I try to use logical operators I have noticed that a standalone logical expression results in T or F as expected. However, if I need the numerical T or F (0 or 1), I get a -1 when logical result is T. For example: integer*4 a a = 1 logicval = (node(5,L).gt.0) numval = 1*(node(5,L).gt.0) write(*,*) logicval, numval would output T, -1 Is there a way in which I can redefine numerical values assigned to T & F? 回答1: Yes

问题 This may be stupid.but i have a simple doubt Suppose i have the following check in a function bool Validate(string a , string b) { if(a == null || b == null) { throw new NullReferenceException(); } else { } } Is it ok to use bitwise OR for validation as shown below if(a == null | b == null) 回答1: In boolean expressions (rather than integers etc), the main difference is: short-circuiting. || short-circuits. | does not. In most cases you want short-circuiting, so || is much much more common. In

问题 I want to make a condition where all selected variables are not equal. My solution so far is to compare every pair which doesn't scale well: if A!=B and A!=C and B!=C: I want to do the same check for multiple variables, say five or more, and it gets quite confusing with that many. What can I do to make it simpler? 回答1: Create a set and check whether the number of elements in the set is the same as the number of variables in the list that you passed into it: >>> variables = [a, b, c, d, e] >>>

问题 Is there any operator or trick for such operation? Or is it necessary to use if(5<i && i<10) ? 回答1: There is no such thing in Java (unless you work with booleans). The 5<i results in a boolean on the left side on <10 which the compiler dislikes. 回答2: You cannot chain inequalities. You can, however, define a static boolean method isInRange(value, low, high) that will perform such a check. Some other languages, like Python or Icon, allow this notation. 回答3: You can use a single comparison but

问题 Is there any operator or trick for such operation? Or is it necessary to use if(5<i && i<10) ? 回答1: There is no such thing in Java (unless you work with booleans). The 5<i results in a boolean on the left side on <10 which the compiler dislikes. 回答2: You cannot chain inequalities. You can, however, define a static boolean method isInRange(value, low, high) that will perform such a check. Some other languages, like Python or Icon, allow this notation. 回答3: You can use a single comparison but

问题 I want to combine the following two IF statements in excel but I was not able to do so. I have tried to use IF , AND , OR statements with no luck. =IF(C98="CAB",D98*R1-F98,F98-D98*S1) =IF(C99="CAB",I99*R6-D99,F99-I99*S6) Once I want to combine the two I get you are trying to create too many arguments. Thanks, Jay 回答1: If you want to combine formulas and according to your last comment, it looks like you are trying to do something like this: =if(condition="CAD",perform Calculation,If(Condition=

问题 I have a function that returns a double value. In some cases the result is zero, and this results should be handled in the caller routing accordingly. I was wondering what is the proper way of returning zero (NaN, false, etc!) in place of double value number: double foo(){ if (some_conditions) { return result_of_calculations; } else { // Which of the following is better? return std::numeric_limits<double>::quiet_NaN(); // (1) return 0; // (2) return false; // (3) return (int) 0; // (4) } }

问题 I'm trying to use only AND OR XOR and NOT to determine whether adding 2 binary number made of 4 bits will overflow. I know, for example, that something like 1100 + 0100 will wind up as 1 | 0000. But how can I find this using just these logical operators? I'm trying to get 1000 when overflow happens, and 0000 when it doesn't. This is easy enough since I can just use XOR with a mask to clear the last 3 bits. Does anyone have suggestions for figuring this out? 回答1: Numbers are ABCD and EFGH, ^

问题 I've tried to come up with a simple solution to the followig problem. Here is the minimum working example: data <- data.frame(subject = c('Math', 'English', 'French', 'English'), grade = c(1, 3, 5, 4)) I want a function that compares Enlish grades and returns a logical vector that has TRUE for the row with the highest english grade, and FALSE for all other rows. In this case [1] FALSE FALSE FALSE TRUE . 回答1: We can get the max 'grade' per 'subject' with ave compare it with the 'grade' to get