First-class functions can be assigned to variables, passed to other functions as arguments, or returned from other functions. The ability to return a function enables deferred execution. Functions that accept other functions as arguments are called higher-order functions.
Questions tagged [first-class-functions]
132 questions
7
votes
2 answers
Dynamic function call in Go
I'm trying to dynamically call functions returning different types of struct.
For example, let's take the following code.
struct A {
Name string
Value int
}
struct B {
Name1 string
Name2 string
Value float
}
func doA() (A) {
…
Eric
- 256
- 1
- 3
- 8
7
votes
1 answer
Does a language with first-class functions necessarily allow closures?
I understand the broad concept of a closure (functions are stored along with a snapshot of environment at the time they were defined), and functions as first class citizens means that functions can be passed and returned like any other data type in…
ffledgling
- 11,502
- 8
- 47
- 69
6
votes
1 answer
passing functions as arguments in clojure
I have a function which takes a function and a number and returns the application of the function on the number, and a cube function:
(defn something [fn x]
(fn x))
(defn cube [x]
(* x x x))
When I call the function as follows it…
Pranav
- 3,340
- 8
- 35
- 48
6
votes
1 answer
alternate ways to implement observer pattern in python
i was going through a post post about how observer pattern can be implemented in python . on the same post there are these comments.
1) In python you may as well just use plain functions, the ‘Observer’
class isnt really needed.
2) This is great…
anekix
- 2,393
- 2
- 30
- 57
5
votes
2 answers
Can function templates be used as first class citizens in higher order function calls?
Passing a function template as argument to another function template is always a bit tricky. Typically one has to resort to creating a lambda object that goes and calls the original function.
Example
template
void f(It, It) {}
void…
bitmask
- 32,434
- 14
- 99
- 159
5
votes
2 answers
Are Kotlin functions really first class types?
Does the fact that this doesn't compile mean that they're not quite first class types?
fun foo(s: String): Int = s.length
// This won't compile.
val bar = foo
Is there a way to do this without resorting to OO?
F. P. Freely
- 1,026
- 14
- 24
5
votes
2 answers
Can I create an anonymous on-the-fly class (implementation of an interface) in C++
In C++, can I create an implementation of an interface on the fly (which ideally binds local-scope variables.) Not sure how to explain it better, so I will put down what I would like the code to look like (roughly):
// Given the following:
class…
nappyfalcon
- 909
- 1
- 10
- 17
5
votes
1 answer
Error using "apply" function in Clojure: "Don't know how to create ISeq from: java.lang.Long"
Working on the following example in "Clojure in Action" (p. 63):
(defn basic-item-total [price quantity]
(* price quantity))
(defn with-line-item-conditions [f price quantity]
{:pre [(> price 0) (> quantity 0)]
:post [(> % 1)]}
…
dtg
- 1,803
- 4
- 30
- 44
4
votes
3 answers
How many of these points in the definition of a first-class element do Java's functions satisfy?
Structure and Interpretation of Computer Programs gives the following as the conditions that an element of a programming language must satisfy to be considered first-class:
They may be named by variables.
They may be passed as arguments to…
J. Mini
- 1,868
- 1
- 9
- 38
4
votes
2 answers
In Julia, why do scope rules for functions appear inconsistent compared to other first class objects?
The Julia docs state that functions are first class objects. I understand that to mean that I ought to be able to use and define them in the same way I would plain old data types.
I'm therefore surprised that
function a(b::Int64)
if b > 0
…
hjab
- 163
- 6
4
votes
1 answer
Setting attributes on a method after class creation raises "'instancemethod' object has no attribute" but the attribiute is clearly there
In Python (2 and 3) we can assign attributes to function:
>>> class A(object):
... def foo(self):
... """ This is obviously just an example """
... return "FOO{}!!".format(self.foo.bar)
... foo.bar = 123
...
>>> a = A()
>>>…
frnhr
- 12,354
- 9
- 63
- 90
4
votes
2 answers
Callback functions in TypeScript
I'm just getting started with Angular 2 and TypeScript and I can't seem to figure out how to use callback functions, I know this may be a silly question but given this regular javascript code:
someOnject.doSomething('dsadsaks', function(data){
…
Leonardo Jines
- 360
- 5
- 17
4
votes
2 answers
Can Functions Be Created at Run-time in Javascript?
Wikipedia's article on first-class citizens states that "some authors" believe functions are only first-class citizens in a language if the language supports their creation at run-time. This article written by James Coglan plainly calls functions…
Thomas
- 6,291
- 6
- 40
- 69
3
votes
2 answers
Desugar Lua operators
Since Lua supports first-class functions, I'd like to know if you can desugar operators, like in many functional languages. E.g in OCaml you can do:
let x = (+) 3 5
The code above inits the variable x with the value 3 + 5. Writing (+) is equivalent…
elmattic
- 12,046
- 5
- 43
- 79
3
votes
1 answer
When using a function as a first-class value in Typescript, is there a way to pass Generic bindings?
I am attempting to wrap typescript functions, returning new functions that add extra behaviour. For example, in the minimal repro below, (see playground) the function after wrapping always returns a Promise and its arguments and return value are…
cefn
- 2,895
- 19
- 28