Applying one function to the result of another is known as function composition: `(f.g)(x) = f(g(x))`
Applying one function to the result of another is known as function composition: (f.g)(x) = f(g(x)).
See also pointfree.
Questions tagged [function-composition]
420 questions
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2 answers
"Adding" two functions together in Scheme
I am going through a practice exam for my programming languages course. One of the problems states:
Define a function named function+ that “adds” two functions together and returns this composition. For example:
((function+ cube double) 3)
should…
Ashley
0
votes
1 answer
Compiler error when using function composition: Cannot convert value of type `([Character]) -> String` to expected > argument type `_ -> _`
I am playing around with the custom operator >>> for function composition that is suggested here.
I have defined the following:
infix operator >>> { associativity left }
func >>> (f: B -> C, g: A -> B) -> (A -> C) {
return { x in…
nburk
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Carrying state/IO through a chain of functions in Clojure to be used later in the chain
I've got a bit of a functional question.
If I have a functional chain where I compose functions in a way that the output of the previous is the input of the next one.
And somewhere down that chain, I need stuff to do IO, like a client to a DB,…
Didier A.
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3 answers
Why does feeding init to last not work in Haskell?
So I'm writing a line to get the second to last element of a list. Initially my code was
mySLast x = last.take ((length x) - 1) x
Which worked up until the last function. Realized the my take business is already included in Haskell as init so I…
Tshimanga
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Composing two functions in R gives different result than a new function enclosing both
I tried to look at the logistic map
logMap <- function(x){
r <- 0.5
4*r*x*(1-x)}
and its compositions such as:
logMap2_a <- function(x){
logMap(logMap(x))}
Of course, you can also directly write a new function that composes logMap with…
networker
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Problems wirh function composition in Haskell
So... I have written this to get 5 rectangles from user :
rectangles <- sequence . take 5 . cycle [getRect]
But it doesn't work. Then I have refactored it as this which is shorthand for writing braces:
rectangles <- sequence $ take 5 $ cycle…
Reygoch
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2 answers
How can I define a function that applies the composition of three functions to a value?
I've got the following question, and I have no idea where to start:
Write a function
trifecta :: (a -> b) -> (b -> c) -> (c -> d) -> a -> d
that takes 3 functions and composes them into a function that takes a value and produces a value. When…
Amr Hamada
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2 answers
Applying properties of a base type to a subtype in JavaScript
I would like to include the properties and initialization logic from a "base" type into a "sub" type in JavaScript. Is the following idiomatic?
function Base(arg1) {
this.foo = arg1.foo;
}
function Sub(arg1) {
//Initialize using the base…
Ben Aston
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1 answer
How do I stay DRY with Meteor template helpers function composition?
I want to remain DRY with my templates so I created some amazing composable functions and helpers only to realize that Spacebars doesn't play nicely.
I have 2 functions that both take two arguments: func(a,b) which in Spacebars turns into {{func a…
Chet
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1 answer
Implementing revmap function with pattern matching or function composition
Higher order function map Definition:
map :: (a -> b) -> [a] -> [b]
map f [] = []
map f (x:xs) = f x:map f xs
Then how to write a revmap function with pattern matching/ using function composition?
Panini
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votes
1 answer
Haskell: Partially applied function, function composition in a raytracer program
I have a problem understanding the function composition and the concept of partially applied functions.
Actually I'm writing a small raytracer and have some example implemenentations which I dont understand exactly. Here is one example which I dont…
Matthias Preu
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0 answers
How to write general integration function in OCaml
I would like to write a function in OCaml that will calculate the definite integral for the given function. The problem is that I aim for the following syntax:
let sphere r phi theta = r *. sin phi *. cos theta in
let dphi = 10 in (* number of parts…
Bartek Chaber
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2 answers
How can I make type inference work with partial functions
I would like to define a class hierarchy of classes that handle messages using a partial function. Each class should defer messages that it can not handle to its superclass. Something like this:
type Respond = PartialFunction[String,…
Rüdiger Klaehn
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1 answer
prevent scala function composition from inferring ? type
I'm trying to compose some functions with compound types in their type parameters:
trait Contains[T]
trait Sentence
trait Token
def sentenceSegmenter[T] = (c: Contains[T]) => null: Contains[T with Sentence]
def tokenizer[T <: Sentence] = (c:…
Steve
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1 answer
How to change the wrapped action call during action composition in play framework 2.0
From what I understand of Action composition, we can wrap multiple action classes around an action class so that the wrapped classes are called first before the action action class
so, for eg:
@With(a.class, b.class)
public static Result index() {
…
Tapan Nallan
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