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
1
vote
3 answers
Multiple commands in one, Matlab
Sometimes it is desired to make several calls in one command. A simple example could be strrep. Assume you want to replace all parentheses with brackets, all commas with dots and then remove all double quotations. The following pseudo code could…
jkazan
- 1,149
- 12
- 29
1
vote
1 answer
Divide and conquer for function compositions
I was searching the algorithm for finding the composition of 2 linear functions n times (where n can be as large as 10^18) in O(log n) time. I just got a pdf containing polynomial composition of 2 functions with large degrees using divide and…
likecs
- 353
- 2
- 13
1
vote
2 answers
Not Function And Function Composition in F#
Is it possible it F# to have function composition between Operators.Not and some standard .NET function, for instance String.IsNullOrEmpty?
In other words, why is the following lambda expression unacceptable:
(fun x -> not >> String.IsNullOrEmpty)
ax1mx2
- 654
- 1
- 11
- 23
1
vote
1 answer
Haskell: nested parens vs. dot notation
Problem 2 of Project Euler says:
Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
By considering the terms in the…
Mark Karavan
- 2,654
- 1
- 18
- 38
1
vote
2 answers
Beginning Haskell - composing function with data constructor and IO monad
I have the following:
import Data.List
data Content
= TaggedContent (String, [String]) String
| Null
processContent :: Content -> IO Content
processContent c@(TaggedContent (id, attrs) text) =
case stripPrefix "include=" a of
Just f …
cm007
- 1,352
- 4
- 20
- 40
1
vote
2 answers
Clojure filter composition with reduce
I have a higher order predicate
(defn not-factor-of-x? [x]
(fn [n]
(cond
(= n x) true
(zero? (rem n x)) false
:else true)))
which returns a predicate that checks if the given argument n is not a factor of x.
Now I want to…
Async
- 13
- 4
1
vote
1 answer
Don't know how to use . and $ operator in Haskell
I am not sure how to implement the . and the $ operators to simplify the following definitions:
compress :: [Char] -> [Char]
compress [] = []
compress as
| g as 1 == 1 = [head as] ++ compress (drop 1 as)
| otherwise = [head as] ++ show (g as…
jchen114
- 25
- 4
1
vote
4 answers
Whats going on with the dot (.) in Haskell?
I'm having trouble understanding how the function composition operator works in Haskell. I understand it in simple cases where you only use functions that takes one argument but I don't understand whats going on when you use it on several functions…
Alex
- 731
- 1
- 11
- 24
1
vote
1 answer
Compose in JavaScript, not applying functions correctly?
Here's my compose function, as a polyfill
Function.prototype.compose = function(prevFunc) {
var nextFunc = this;
return function() {
return nextFunc.call(this, prevFunc.apply(this,arguments));
}
}
These work:
function…
Dan Mantyla
- 1,840
- 1
- 22
- 33
1
vote
3 answers
Haskell : why f1 . f2 xy not working?
I'm a bit confused concerning the dot operator. I've got the following code (for testing):
test :: Int -> Int -> Int
test x y = f1 . f2 x y
where f1 n = n+1
f2 x' y' = x' * y'
And I figured it would first execute (f2 x…
user2999349
- 859
- 8
- 21
1
vote
1 answer
Why do I get a parse error on '='
I am currently working 99 haskell problems
I cannot understand why am I getting an error in this function :-
repli :: [a] -> Int -> [a]
repli xs n = concatMap (take n . repeat) xs
Ada Xu
- 953
- 4
- 14
- 31
1
vote
1 answer
Clojure: function composition at runtime
Problem:
Suppose I have a set of functions f_1 ... f_n that I want to compose at runtime, such that I get for example:
(f_a (f_b (f_c) (f_d)) (f_e))
Therefore I need the types of the parameters and the return value of each function in order to…
MLmuchAmaze
- 379
- 2
- 14
1
vote
4 answers
Is there a way to inject a try catch inside a function?
Maybe some of you know about AOP, in some languages using AOP can lead you to be able to inject code after, before, or while a method is executing,etc.
What I want is to apply the same in Javascript, I am currently working on a massive app which has…
Bryan Arbelo - MaG3Stican
- 2,174
- 7
- 28
- 55
1
vote
0 answers
Calculating the expected value of a transformed random variable in MATLAB?
I am trying to compute the following expected value for Z being lognormally distributed
E[Z^eta w(F_Z (Z))^-eta]
where eta is a real number, F_Z the distribution function of Z and w:[0,1]->[0,1] an increasing function.
First of all, I am pretty new…
Tim
- 11
- 1
1
vote
3 answers
JavaScript: Successively calling a list of functions on an object
Let's say I have a list of functions stored in an array:
var myFunctions = [
function (i) {return i + 2},
function (i) {return i * 2},
function (i) {return i - 3}
]
What would be the best way to successively call all these functions an…
Sacha
- 1,987
- 1
- 24
- 41