Yes, actually you can take some code and convert every function call—and every return—into a tail call. What you end up with is called continuation-passing style, or CPS. For example, here’s a function containing two recursive calls: (define (count-tree t) (if (pair? t) (+ (count-tree (car t)) (count-tree (cdr t))) 1)) And here’s how it … Read more
It is quite possible in python 3 thanks to the magic of nonlocal. def foo(): var_a = 2 var_b = 3 def _closure(x, magic = None): nonlocal var_a if magic is not None: var_a = magic return var_a + var_b + x return _closure localClosure = foo() # Local closure is now “return 2 + … Read more
See also Odersky et al.’s paper “Deprecating the Observer Pattern“. It explains the library Scala.React, which was developed for the paper.
You can modify your solution to collect the Stream of String arrays into a Map (instead of using forEach) : Map<String, Double> kvs = Arrays.asList(“a:1.0”, “b:2.0”, “c:3.0”) .stream() .map(elem -> elem.split(“:”)) .collect(Collectors.toMap(e -> e[0], e -> Double.parseDouble(e[1]))); Of course this solution has no protection against invalid input. Perhaps you should add a filter just in … Read more
FunctionalJava is the best known library; it makes use of Java closures (BGGA) for examples: final Array<Integer> a = array(1, 2, 3); final Array<Integer> b = a.map({int i => i + 42}); arrayShow(intShow).println(b); // {43,44,45} EDIT Check also lambdaj. Further EDIT BGGA is entirely optional. It just makes for nicer syntax.
I’m glad you’re starting by asking about a specification rather than implementation first. There are a lot of ideas floating around about what FRP is. From the very start in the early 90’s (when I was working in interactive graphics at Sun Microsystems and then Microsoft Research), it has been about two properties (a) denotative … Read more
A lens consists of two functions, a getter and a setter: data Lens a b = Lens { getter :: a -> b, setter :: b -> a -> a } For example, we might have lenses for the first and second parts of a pair: fstLens :: Lens (a, b) a fstLens = Lens … Read more
Test-driven developers should feel right at home in functional languages like F#: small functions that give deterministically repeatable results lend themselves perfectly to unit tests. There are also capabilities in the F# language that facilitate writing tests. Take, for example, Object Expressions. You can very easily write fakes for functions that take as their input … Read more
Dart v1.23 added a new syntax for writing function types which also works in-line. void doSomething(Function(int) f) { f(123); } It has the advantage over the function-parameter syntax that you can also use it for variables or anywhere else you want to write a type. void doSomething(Function(int) f) { Function(int) g = f; g(123); } … Read more
One can create an empty array, fill it (otherwise map will skip it) and then map indexes to values: Array(8).fill(0).map((_, i) => i * i);