Functional programming is a paradigm which attempts to solve computational problems by the chained evaluation of functions whose output is determined by their inputs rather than the programme state. In this style of programming, side effects and mutable data are deprecated and usually strictly ...

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Can objects be implemented in terms of higher order functions?

Martin Odersky finished one online course on Scala with an unanswered question: Can we implement one concept in terms of other ? Objects in terms of higher order functions? Higher order functions ...
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1answer
204 views

How do I create my own Objective-C to Swift converter? [closed]

I'm really interested in writing my own converter. I know C++/Python/Objective-C/Swift and a little Haskell. There are website like objectivec2swift and iswift.org, which can convert OC to Swift ...
8
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2answers
346 views

Workaround for implementing operations on doubly linked or circular data structures in languages with immutable data

I would like to learn how to make graphs and perform some local operations on them in Haskell, but the question is not specific to Haskell, and instead of graphs we may consider doubly linked lists. ...
14
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4answers
802 views

APIs and functional programming

From my (admittedly limited) exposure to functional programming languages, such as Clojure, it seems that encapsulation of data has a less important role. Usually various native types such as maps or ...
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1answer
142 views

Comparison Function Returns True or False

In my python CS class at school, we were given a true or false question as follows. A comparison function returns either True or False. When originally answering I thought about two things. ...
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3answers
267 views

Function Overloading in Python

My book says that function overloading is not possible in python but it asks me questions like: WAP to find out the volume of a cube,cuboid and cylinder using function overloading. Do I have to ...
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4answers
637 views

How does “repeat x = x:repeat x” return a list in Haskell?

This is supposed to return an infinite list of x's. However a list is created using an element, then the operator ':' and then a list. The recursive definition of repeat' x = x:repeat' x seems to ...
19
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3answers
6k views

Why would I not need an ORM in a functional language like Scala?

I'm wondering if I can switch from Java to Scala in a Spring + Hibernate project to take advantage of some Scala features such as pattern matching, Option and what it seems to me a cleaner syntax in ...
4
votes
2answers
734 views

What are functional programmers using in place of UML?

I'm CS student. I am currently attending lectures, where we're taught Objective Analysis and Design. It consists mostly of writing use cases, analysing the problem that we can face when writing some ...
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1answer
874 views

Are the paradigms of ReactJS and Redux worthwhile for things other than web-development?

I'm a bit fascinated by the current paradigms shift libraries like ReactJs and Redux have caused in web development. Apart from computer science classes, I wasn't much affected by functional ...
7
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2answers
141 views

Is the Perl default variable like an FP monad?

I have been getting my head around monads in functional programming and seem to see some commonality between Perl's default variable $_ and FP monads. Is this true? Are there similarities, if not ...
3
votes
3answers
120 views

Split a File into Multiple Objects Functionally

I want to read a file into a collection of objects. The data (it's a Leica PTX file if you're curious) is formatted as follows: 640 [begin item #1: number of columns] 480 [number of rows] 0 0 0 [...
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5answers
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Is a function immediately impure if it takes a function as a parameter?

Since the purity of an input parameter is an unknown until runtime, is a function immediately considered impure if it takes a function as an input parameter? Related: if a function applies a pure ...
2
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3answers
213 views

Functional programming: Compare all items in an array

In functional programming, how do I do an equality comparison of all items in an array? I have an array of items that I want to compare, for example for equality. Is it possible to use a fold (also ...
4
votes
1answer
154 views

If Java allows immutable classes, then why cannot it be used as a functional language [closed]

I have been struggling with functional programming concepts for a while. I read that in functional programming, variable immutability is a fundamental thing. You don't change the state of a variable. ...
10
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2answers
1k views

Functional programming, compared to the process of a computer [duplicate]

In functional programming, it is considered bad practice (at least from my observations) to use state changes. Since computers operate in an imperative-language-like matter (performing one operation ...
2
votes
1answer
82 views

Time complexity of update and lookup in binary random access list

I'm trying to get through one of the exercises in Okasaki's "Purely Functional Data Structures," where he presents a zeroless binary numbers as a structure for random-access list, and asks to 9.6 ...
19
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2answers
460 views

How different is garbage collection in pure languages?

In a pure language like Haskell, all data is immutable and no existing data structures can be changed in any way. Additionally, many algorithms on immutable data and functional programming patterns ...
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2answers
758 views

Why do Haskell and Scheme use singly-linked lists?

A doubly linked list has minimal overhead (just another pointer per cell), and allows you to append to both ends and go back and forth and generally have a lot of fun.
3
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2answers
291 views

Shared data in functional programming

I have been working on a project in JavaScript which requires a data structure (read only), to be shared between two functions. var mySharedData = ['hours', 'minutes', 'seconds']; Now I have two ...
3
votes
3answers
367 views

How does Functional Programming's immutability feature work with CQS?

Given immutability (which is often encouraged and said to be one of building blocks of functional programming) and CQS (which says that commands should not return a value other than void/unit), how do ...
29
votes
5answers
4k views

What is it about functional programming that makes it inherently adapted to parallel execution? [duplicate]

I've been reading over and over that functional languages are ideal (or at least very often useful) for parallelism. Why is this? What core concepts and paradigms are typically employed and which ...
3
votes
2answers
898 views

Using 'reduce' vs 'for' loop for returning boolean [closed]

I was wondering what people think about using a reduce function vs loop for returning true if a condition exists. Example: var a = [1, 5, 7, 4, 2, 5, 3]; var greaterThan5 = a.reduce(function(prev, ...
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2answers
496 views

Can higher order functions ever be pure?

I was thinking about pure functions especially in the context of C++, which of course is not a purely functional language, and was wondering if higher order functions in C++ can ever be considered ...
6
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3answers
211 views

Why don't “multi-infinite” list comprehensions work with lazy evaluation?

As a simple demonstration of the efficiency of Haskell style, I thoughtlessly ran the following: take 100 [(a, b, c) | a <- [1..], b <- [1..], c <- [1..], a^2 + b^2 == c^2] This should be a ...
2
votes
2answers
390 views

Program like NASA?: Margaret Hamilton's Three Primitive Control Structures [closed]

On slide 19 in a presentation Margaret Hamilton describes three primitive control structures. My goal is to reduce the probability of errors in my code by working with this "design framework". I am ...
2
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1answer
223 views

Patterns for sharing context variables between functions

I am looking for ways of passing around a set of contextual variables that are required by functions. As a Python programmer, right now I can see three ways of solving the problem: passing them ...
3
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2answers
368 views

Does function pointer have the same expressive power as function as parameter?

In functional programming language, a function can be passed as an argument to another function. In programming language like C/C++, a function pointer referring to a function can be passed to a ...
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3answers
338 views

Is the benefit of the IO monad pattern for handling side effects purely academic?

Sorry for yet another FP + side effects question, but I couldn't find an existing one which quite answered this for me. My (limited) understanding of functional programming is that state/side effects ...
8
votes
4answers
359 views

Is there a Haskell idiom for trying several functions and stop as soon as one succeeds?

In Haskell, I can use the type a -> Maybe b to model a function that either returns a value of type b, or returns nothing (it fails). If I have types a1, ..., a(n+1) and functions f1, ..., fn, ...
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1answer
404 views

The difference between bind and _.curry

So JavaScript's bind supports currying, but most people use some other library like lodash or ramda to do currying. From first impression It seems like bind supports context changing, since that is ...
5
votes
2answers
251 views

What is the difference between currying and partial function application in practice

I understand the difference between partial function application and a curried function (f(X x Y x Z) -> N vs f(X -> (Y -> (Z -> N)))), but I do not see what the consequence of this ...
31
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2answers
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What is the meaning of “doesn't compose”?

I see a lot of texts, especially functional programming texts, claim that certain CS concepts "don't compose". Examples are: locks don't compose, monads don't compose. I've been having a hard time ...
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2answers
155 views

Is the function using python list comprehension, stateless?

Below is the function count_leaf, that appends mutable list branch_counts, which is not stateless. def count_leaf(tree): if is_leaf(tree): return 1 branch_counts = list() for b in ...
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0answers
70 views

How to ensure this constraint at compile time?

I have an interesting constraint/invariant and I would love to hear people's input on how to maintain it. Big bonus if it can be ensured at compile time... I have the types below, and the following ...
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2answers
157 views

What is the advantage of global functions when writing functional code

I am a Swift developer and am trying to adopt a functional / reactive style in my code. I have been using ReactiveCocoa in all my projects and I have started giving RAC 3.0 a try. One thing I have ...
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3answers
225 views

Using delegates to avoid duplicate creation of resources

I'm writing a PCL that uses an HttpClient to go visit a few sites and extract data from them. My initial code looked like this: public static class Download { public async static Task<byte[]&...
8
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2answers
309 views

How to handle complex calculated fields in an ORM

In our API we've got a few central datatypes which need to be "decorated" (so to speak) after retrieval from the database with calculated values. The database is accessed through an ORM which follows ...
2
votes
2answers
468 views

How do I make this functional DSL written in an imperative language more efficient?

Suppose I create a simple functional Domain-specific language (DSL) using an imperative language, in this case C++. Here is a simple implementation of a DSL that can has the notion of a simple value ...
16
votes
3answers
2k views

What problem do algebraic data types solve?

Fair warning, I'm new to functional programming so I may hold many bad assumptions. I've been learning about algebraic types. Many functional languages seem to have them, and they are fairly useful ...
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votes
5answers
1k views

Is the semantic contract of an interface (OOP) more informative than a function signature (FP)?

It is said by some that if you take SOLID principles to their extremes, you end up at functional programming. I agree with this article but I think that some semantics are lost in the transition from ...
30
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6answers
6k views

Why do programs use call stacks, if nested function calls can be inlined?

Why not have the compiler take a program like this: function a(b) { return b^2 }; function c(b) { return a(b) + 5 }; and convert it into a program like this: function c(b) { return b^2 + 5 }; ...
5
votes
2answers
264 views

Are (basic) SQL queries semantically equivalent to Higher Order Functions?

Is SQL basically a domain specific instance of map + fold + filter? It seems to me that the following SQL: SELECT name FROM fruits WHERE calories < 100 is just syntactic sugar for the ...
9
votes
1answer
299 views

Is it possible to have currying and variadic function at the same time?

I am thinking about making currying and variadic functions both available in a dynamically-typed functional programming language, but I wonder if it is possible or not. Here are some pseudocode: sum ...
40
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10answers
7k views

Why would a program use a closure?

After reading many posts explaining closures here I'm still missing a key concept: Why write a closure? What specific task would a programmer be performing that might be best served by a closure? ...
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vote
2answers
107 views

distinguish requests from the same vehicle

I am implementing an small app to track buses based on Crowdsorcing. The riders send data long, lat, mac, route to the server as JSON string. In my database I have table bus to insert the transmitted ...
3
votes
1answer
251 views

Why can a constructor be used without `new` keyword in Javascript?

I found Date can be used without the new keyword. Date(1) > "Thu May 28 2015 15:54:20 GMT+0800 (CST)" new Date(1) > Thu Jan 01 1970 08:00:00 GMT+0800 (CST) I was wondering whether there is ...
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2answers
142 views

Functional Programming - Functions defining specific evaluation of functions passed to it for optimization

Firstmost, I am just getting started with functional programming so I would appreciate corrections in any terminology I may have used incorrectly. Story time, While doing a Project Euler Problem 1 in ...
5
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2answers
464 views

How to design for good abstractions using algebraic data type?

Every now and then I have peaked at Haskell Tutorials and found the Algebraic data types quite interesting. I took their purpose to be to represent types that have completely separable states. Sadly, ...
7
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3answers
239 views

What is the functional programming answer to type-based invariants?

I am aware that the concept of invariants exists across multiple programming paradigms. For example, loop invariants are relevant in OO, functional and procedural programming. However, one very ...