I suspect the code you are actually using is not FOO, but foo, lowercase, which will cause Scala to just assign the value to foo, instead of comparing the value to it. In other words: x match { case A => // compare x to A, because of the uppercase case b => // assign … Read more
Structured binding only works if the structure is known at compile time. This is not the case for the vector. While you do know the structure of the individual elements, you do not know the number of elements, and that is what you are trying to decompose on in your question. Similarly, you can only … Read more
You can use record patterns like this: data X = A | B {name :: String} | C {x::Int, y::Int, name::String} myfn :: X -> Int myfn A = 50 myfn B{} = 200 myfn C{} = 500 Record patterns allow you to give names to the fields of the constructors. you can also do … Read more
grep -m2 “two” in-file.txt | tail -n1 Stop after the second match, then take the second line printed.
It’s a known limitation of Rust’s patterns. Method calls (including internal methods for operators like ==) automatically call .deref() as needed, so String gets automagically turned into &str for comparisons with literals. On the other hand, the patterns are quite literal in their comparisons, and find that String and &str are different. There are two … Read more
Guard using Range: val m = t match { case x if 0 until 10 contains x => true case _ => false }
Quick Solution You just need to add parentheses, or begin/end, around the inner match: let rec filter exp = match exp with | Var v -> Var v | Sum (e1, e2) -> Sum (e1, e2) | Prod (e1, e2) -> Prod (e1, e2) | Diff (e1, e2) -> (match e2 with | Sum (e3, … Read more
First, aren’t you supposed to be using vl_sift instead of sift? Second, you can use SIFT feature matching to find correspondences in the two images. Here’s some sample code: I = imread(‘p1.jpg’); J = imread(‘p2.jpg’); I = single(rgb2gray(I)); % Conversion to single is recommended J = single(rgb2gray(J)); % in the documentation [F1 D1] = vl_sift(I); … Read more
This however will compile: def checkType(cls: AnyRef) { cls match { case s: String => println(“is a String”) case d: Date => println(“is a Date”) case _ => println(“others”) } } … or the simplified version of that: def checkType(cls: AnyRef) = cls match { case _: String => println(“is a String”) case _: Date … Read more
To do this with a regex, you will need to iterate over it with .exec() in order to get multiple matched groups. The g flag with match will only return multiple whole matches, not multiple sub-matches like you wanted. Here’s a way to do it with .exec(). var input = “‘Warehouse’,’Local Release’,’Local Release DA'”; var … Read more