comparison

问题 What is the best way for checking empty strings (I'm not asking about initializing!) in C# when considering code performance ?(see code below) string a; // some code here....... if(a == string.Empty) or if(string.IsNullOrEmpty(a)) or if(a == "") any help would be appreciated. :) 回答1: Do not compare strings to String.Empty or "" to check for empty strings. Instead, compare by using String.Length == 0 The difference between string.Empty and "" is very small. String.Empty will not create any

问题 If I compare a string literal to a string literal using the case statement, I get the expected behavior: if they are the same - it matches, if they are not - it does not. However, if I compare a string literal to a constant that is a string, I get "Pattern matches are overlapped" warning and the branch with the constant always matches. Here's an example session: Prelude> let var1 = "abc" Prelude> let var2 = "def" Prelude> case var1 of { var2 -> "Fail"; _ -> "Win" } <interactive>:1:0: Warning:

问题 So far I've seen many posts dealing with equality of floating point numbers. The standard answer to a question like "how should we decide if x and y are equal?" is abs(x - y) < epsilon where epsilon is a fixed , small constant. This is because the "operands" x and y are often the results of some computation where a rounding error is involved, hence the standard equality operator == is not what we mean, and what we should really ask is whether x and y are close , not equal. Now, I feel that if

问题 So far I've seen many posts dealing with equality of floating point numbers. The standard answer to a question like "how should we decide if x and y are equal?" is abs(x - y) < epsilon where epsilon is a fixed , small constant. This is because the "operands" x and y are often the results of some computation where a rounding error is involved, hence the standard equality operator == is not what we mean, and what we should really ask is whether x and y are close , not equal. Now, I feel that if

问题 This question already has answers here : Multiple string comparison with C# (7 answers) Closed last year . I have this piece of code: if (filter != RECENT && filter != TODAY && filter != WEEK && filter != MONTH && filter != ALLTIME) { filter = RECENT; } Note that filter is a string and it's compared against const string types. Is there any way to do this inline and have it be more readable? Doing it with the ternary operator doesn't make it much better since I still have to repeat filter !=

问题 I have two data arrays: $arrnames=('a','b','c') $arrtypes=('x','y','z') and I have a lookup array: $arrlookup=('y','z') I need to return the elements in $arrnames where the matching element in $arrtypes is contained in $arrlookup . I've been playing with foreach looping over $arrnames and looking at the same element in $arrtypes by index but it's getting sloppy and I know there has to be a better way. I've seen some similar questions, but not anything that strikes me as specifically answering

问题 I have two dictionary with multiple items. I want to compare values. Dict1:{ "Displacement_trim" = "49.26 "; "Dry_Weight" = "<null>"; } Dict2:{ "Displacement_trim" = "171.20 "; "Dry_Weight" = "<null>"; } I want to know which "Displacement_trim" is greater. Also checking null values. Print the data in cell. How can I achieve this? 回答1: To find out which value from the dict is bigger use the following code: Swift 3 let dict1 = [ "Displacement_trim" : "49.26", "Dry_Weight" : "<null>" ] let dict2

问题 I'm trying to make a function that will compare multiple variables to an integer and output a string of three letters. I was wondering if there was a way to translate this into Python. So say: x = 0 y = 1 z = 3 mylist = [] if x or y or z == 0 : mylist.append("c") if x or y or z == 1 : mylist.append("d") if x or y or z == 2 : mylist.append("e") if x or y or z == 3 : mylist.append("f") which would return a list of ["c", "d", "f"] Is something like this possible? 回答1: You misunderstand how

问题 I'm trying to make a function that will compare multiple variables to an integer and output a string of three letters. I was wondering if there was a way to translate this into Python. So say: x = 0 y = 1 z = 3 mylist = [] if x or y or z == 0 : mylist.append("c") if x or y or z == 1 : mylist.append("d") if x or y or z == 2 : mylist.append("e") if x or y or z == 3 : mylist.append("f") which would return a list of ["c", "d", "f"] Is something like this possible? 回答1: You misunderstand how

问题 Hi I have a stored procedure which suppose to compare between 2 columns on different tables Users.ID => int Trans.ID => nvarchar Sometimes the value in Trans.ID is not numeric at all, and sometimes it's null, which causes an error while trying to compare is there a way to try to parse Trans.ID into a number and in case it doesn't succeed to return 0?? I tried NullIf() but it doesn't work when the value inside is not numeric. 回答1: you can do something like: select * from users u inner join