tuples

问题 In the simple parser library I am writing, the results of multiple parsers is combined using std::tuple_cat . But when applying a parser that returns the same result multiple times, it becomes important to transform this tuple into a container like a vector or a deque. How can this be done? How can any tuple of the kind std::tuple<A> , std::tuple<A, A> , std::tuple<A, A, A> etc be converted into a std::vector<A> ? I think this might be possible using typename ...As and sizeof ...(As) , but I

问题 In the simple parser library I am writing, the results of multiple parsers is combined using std::tuple_cat . But when applying a parser that returns the same result multiple times, it becomes important to transform this tuple into a container like a vector or a deque. How can this be done? How can any tuple of the kind std::tuple<A> , std::tuple<A, A> , std::tuple<A, A, A> etc be converted into a std::vector<A> ? I think this might be possible using typename ...As and sizeof ...(As) , but I

问题 Say I have a list of tuples, like the following: listo = [('a','1'),('b','0'),('c','2'),('d','0')] If I want the lowest tuple, based on the second index of each tuple, I can customize the min function with a lambda function, like this: min(listo, key=lambda x: x[1]) As it stands, this code would return: In [31]: min(listo, key=lambda x: x[1]) Out[31]: ('b', '0') But this only gives me one tuple, and only the first one it encounters at that. What if I wanted ALL the min tuples? So it returns

问题 Say I have a list of tuples, like the following: listo = [('a','1'),('b','0'),('c','2'),('d','0')] If I want the lowest tuple, based on the second index of each tuple, I can customize the min function with a lambda function, like this: min(listo, key=lambda x: x[1]) As it stands, this code would return: In [31]: min(listo, key=lambda x: x[1]) Out[31]: ('b', '0') But this only gives me one tuple, and only the first one it encounters at that. What if I wanted ALL the min tuples? So it returns

问题 I am implementing function that gets random index and returns the element at random index of tuple. I know that for tuple like, val a=(1,2,3) a._1=2 However, when I use random index val index=random_index(integer that is smaller than size of tuple) , a._index doesnt work. 回答1: You can use productElement, note that it is zero based and has return type of Any : val a=(1,2,3) a.productElement(1) // returns 2nd element 回答2: If you know random_index only at runtime the best what you can have is

问题 Is it possible to deconstruct a tuple in C#, similar to F#? For example, in F#, I can do this: // in F# let tupleExample = (1234,"ASDF") let (x,y) = tupleExample // x has type int // y has type string Is it possible to do something similar in C#? e.g. // in C# var tupleExample = Tuple.Create(1234,"ASDF"); var (x,y) = tupleExample; // Compile Error. Maybe I can do this if I use an external library, e.g. LINQ??? Or do I have to manually use Item1, Item2? e.g. // in C# var tupleExample = Tuple

问题 scala> val two = (1,2) two: (Int, Int) = (1,2) scala> val one = (1,) <console>:1: error: illegal start of simple expression val one = (1,) ^ scala> val zero = () zero: Unit = () Is this: val one = Tuple1(5) really the most concise way to write a singleton tuple literal in Scala? And does Unit work like an empty tuple? Does this inconsistency bother anyone else? 回答1: really the most concise way to write a singleton tuple literal in Scala? Yes. And does Unit work like an empty tuple? No, since

问题 scala> val two = (1,2) two: (Int, Int) = (1,2) scala> val one = (1,) <console>:1: error: illegal start of simple expression val one = (1,) ^ scala> val zero = () zero: Unit = () Is this: val one = Tuple1(5) really the most concise way to write a singleton tuple literal in Scala? And does Unit work like an empty tuple? Does this inconsistency bother anyone else? 回答1: really the most concise way to write a singleton tuple literal in Scala? Yes. And does Unit work like an empty tuple? No, since

问题 scala> val two = (1,2) two: (Int, Int) = (1,2) scala> val one = (1,) <console>:1: error: illegal start of simple expression val one = (1,) ^ scala> val zero = () zero: Unit = () Is this: val one = Tuple1(5) really the most concise way to write a singleton tuple literal in Scala? And does Unit work like an empty tuple? Does this inconsistency bother anyone else? 回答1: really the most concise way to write a singleton tuple literal in Scala? Yes. And does Unit work like an empty tuple? No, since

问题 scala> val two = (1,2) two: (Int, Int) = (1,2) scala> val one = (1,) <console>:1: error: illegal start of simple expression val one = (1,) ^ scala> val zero = () zero: Unit = () Is this: val one = Tuple1(5) really the most concise way to write a singleton tuple literal in Scala? And does Unit work like an empty tuple? Does this inconsistency bother anyone else? 回答1: really the most concise way to write a singleton tuple literal in Scala? Yes. And does Unit work like an empty tuple? No, since