functional-programming
Why does OCaml sometimes require eta expansion?
What you got here is the value polymorphism restriction of ML language family. The aim of the restriction is to settle down let-polymorphism and side effects together. For example, in the following definition: let r = ref None r cannot have a polymorphic type ‘a option ref. Otherwise: let () = r := Some 1; … Read more
In C, what is the difference between `&function` and `function` when passed as arguments?
There is no difference. For evidence see the C99 specification (section 6.7.5.3.8). “A declaration of a parameter as ‘‘function returning type’’ shall be adjusted to ‘‘pointer to function returning type’’, as in 6.3.2.1.”
Is it possible to get next element in the Stream?
No, this is not possible using streams, at least not easily. The stream API abstracts away from the order in which the elements are processed: the stream might be processed in parallel, or in reverse order. So “the next element” and “previous element” do not exist in the stream abstraction. You should use the API … Read more
So: what’s the point?
If you already have a b : Bool, you can turn it into proposition: So b, which is a bit shorther than b ≡ true. Sometimes (I don’t remember any actual case) there is no need to bother with a proper data type, and this quick solution is enough. So seems to have serious disadvantages … Read more
whats the difference between function foo(){} and foo = function(){}? [duplicate]
No, they’re not the same, although they do both result in a function you can call via the symbol foo. One is a function declaration, the other is a function expression. They are evaluated at different times, have different effects on the scope in which they’re defined, and are legal in different places. Quoting my … Read more
Purpose of third argument to ‘reduce’ function in Java 8 functional programming
Are you talking about this function? reduce <U> U reduce(U identity, BiFunction<U,? super T,U> accumulator, BinaryOperator<U> combiner) Performs a reduction on the elements of this stream, using the provided identity, accumulation and combining functions. This is equivalent to: U result = identity; for (T element : this stream) result = accumulator.apply(result, element) return result; but … Read more
Idiomatic Way to declare C++ Immutable Classes
The way you proposed is perfectly fine, except if in your code you need to make assignment of RockSolid variables, like this: RockSolid a(0,1); RockSolid b(0,1); a = b; This would not work as the copy assignment operator would have been deleted by the compiler. So an alternative is to rewrite your struct as a … Read more
Using partial functions in Scala – how does it work?
A partial function is a function that is valid for only a subset of values of those types you might pass in to it. For example: val root: PartialFunction[Double,Double] = { case d if (d >= 0) => math.sqrt(d) } scala> root.isDefinedAt(-1) res0: Boolean = false scala> root(3) res1: Double = 1.7320508075688772 This is useful … Read more
Ruby’s yield feature in relation to computer science
Ruby’s yield is not an iterator like in C# and Python. yield itself is actually a really simple concept once you understand how blocks work in Ruby. Yes, blocks are a functional programming feature, even though Ruby is not properly a functional language. In fact, Ruby uses the method lambda to create block objects, which … Read more