ternary

问题 I have the following code: class A { public: operator int() const { return 5; } }; class B { public: operator int() const { return 6; } }; int main() { A a; B b; int myInt = true ? a : b; return 0; } Attempting to compile that code with Visual Studio 2017 RC results in the following error: error C2446 : : : no conversion from B to A note: No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called ...which is surprising because I would

问题 I've an expression of the form shown below :- while (count) { ... ... index = ((count == 20)? 0 : index++); ... ... } Now Ternary operators are sequence points in C but I believe that the sequence point ends at the test part. Is this understanding correct and as such will this statement lead to undefined behaviour ? 回答1: Right. There's a sequence point after the evaluation of the condition, but the next sequence point is the semicolon terminating the statement. So whenever count != 20 , you

问题 I'm trying to come up with a way of plotting a ternary heatmap using R. I think ggtern should be able todo the trick, but I don't know how to do a binning function like stat_bin in vanilla ggplot2. Here's What I have so far: require(ggplot2) require(ggtern) require(MASS) require(scales) palette <- c( "#FF9933", "#002C54", "#3375B2", "#CCDDEC", "#BFBFBF", "#000000") sig <- matrix(c(1,2,3,4),2,2) data <- data.frame(mvrnorm(n=10000, rep(2, 2), Sigma)) data$X1 <- data$X1/max(data$X1) data$X2 <-

问题 This question already has answers here : Why can't we have return in the ternary operator? (4 answers) Closed 7 months ago . I need to return true or false if an option in a drop down selected. This is my code: var active = sort.attr('selected') ? return true : return false; I get an error that the first return is unexpected. Why? 回答1: You cannot assign a return statement to a variable. If you want active to be assigned the value true or false , just delete the return s: var active = sort

问题 Imagine I have a class Family. It contains a List of Person. Each (class) Person contains a (class) Address. Each (class) Address contains a (class) PostalCode. Any "intermediate" class can be null. So, is there a simple way to get to PostalCode without having to check for null in every step? i.e., is there a way to avoid the following daisy chaining code? I know there's not "native" Java solution, but was hoping if anyone knows of a library or something. (checked Commons & Guava and didn't

问题 Users, I'd like to have some tips for a ternaryplot ("vcd"). I have this dataframe: a <- c(0.1, 0.5, 0.5, 0.6, 0.2, 0, 0, 0.004166667, 0.45) b <- c(0.75,0.5,0,0.1,0.2,0.951612903,0.918103448,0.7875,0.45) c <- c(0.15,0,0.5,0.3,0.6,0.048387097,0.081896552,0.208333333,0.1) d <- c(500,2324.90,2551.44,1244.50, 551.22,-644.20,-377.17,-100, 2493.04) df <- data.frame(a, b, c, d) and I'm building a ternary plot: ternaryplot(df[,1:3], df$d) How can I map the continuous variable d , obtaining a result

问题 Users, I'd like to have some tips for a ternaryplot ("vcd"). I have this dataframe: a <- c(0.1, 0.5, 0.5, 0.6, 0.2, 0, 0, 0.004166667, 0.45) b <- c(0.75,0.5,0,0.1,0.2,0.951612903,0.918103448,0.7875,0.45) c <- c(0.15,0,0.5,0.3,0.6,0.048387097,0.081896552,0.208333333,0.1) d <- c(500,2324.90,2551.44,1244.50, 551.22,-644.20,-377.17,-100, 2493.04) df <- data.frame(a, b, c, d) and I'm building a ternary plot: ternaryplot(df[,1:3], df$d) How can I map the continuous variable d , obtaining a result

问题 I tripped across a really strange NullPointerException the other day caused by an unexpected type-cast in the ternary operator. Given this (useless exemplary) function: Integer getNumber() { return null; } I was expecting the following two code segments to be exactly identical after compilation: Integer number; if (condition) { number = getNumber(); } else { number = 0; } vs. Integer number = (condition) ? getNumber() : 0; . Turns out, if condition is true , the if -statement works fine,

问题 I tripped across a really strange NullPointerException the other day caused by an unexpected type-cast in the ternary operator. Given this (useless exemplary) function: Integer getNumber() { return null; } I was expecting the following two code segments to be exactly identical after compilation: Integer number; if (condition) { number = getNumber(); } else { number = 0; } vs. Integer number = (condition) ? getNumber() : 0; . Turns out, if condition is true , the if -statement works fine,

问题 I have this code: if (providers.length > 0) this.providers = providers; else throw new IllegalArgumentException(); And i want to simplify it. I went for: (providers.length > 0) ? this.providers = providers : throw new IllegalArgumentException(); But that gives me a compiler error. Why? 回答1: The reason why the ternary operator doesn't work is because that is for assigning values. Meaning: the "else" part after ":" needs to return a value of the same type as the "then" case after "?". And throw