What are the best languages for learning functional programming?

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22

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568

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Recs.

Oct 16, 2018

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Here’s the Deal

The Best 2 of 22 OptionsWhy?

Best languages for learning functional programming	Price	Site	Current stable version
93 Elm	-	http://elm-lang.org/	0.18
90 Haskell	-	https://www.haskell.org/	https://www.haskell.org/
84 Clojure	-	www.clojure.org	1.9
84 Elixir	-	https://elixir-lang.org	1.6
79 Scheme	-	–	–

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Haskell

Top Pro

Forces you to learn pure functional programming

It is pure and does not mix other programming paradigms into the language. This forces you to learn functional programming in its most pure form. You avoid falling back on old habits and learn an entirely new way to program. See More

Top Con

Difficult learning curve

Haskell lends itself well to powerful abstractions - the result is that even basic, commonly used libraries, while easy to use, are implemened using a vocabularly that requires a lot of backround in abstract mathematics to understand. Even a concept as simple as "combine A and B" is often, both in code and in tutorials, described in terms of confusing and discouraging terms like "monad", "magma", "monoid", "groupoid", and "ring". This also occasionally bears its ugly head in the form of complicated error messages from type inference. See More

Specs

Site:https://www.haskell.org/

Top Pro

Open source

All Haskell implementations are completely free and open source. See More

Top Con

Language Extensions lead to unfamiliar code

Haskell's language extensions, while making the language incredibly flexible for experienced users, makes a lot of code incredibly unfamiliar for beginners. Some pragmas, like NoMonomorphismRestriction, have effects that seem completely transparent in code, leading beginners to wonder why it's there. Others, like ViewPatterns, and particularly TemplateHaskell, create completely new syntax rules that render code incomprehensible to beginners expecting vanilla function application. See More

Top Pro

Mathematical consistency

As Haskell lends itself exceedingly well to abstraction, and borrows heavily from the culture of pure mathematics, it means that a lot more code conforms to very high-level abstractions. You can expect code from vastly different libraries to follow the same rules, and to be incredibly self-consistent. It's not uncommon to find that a parser library works the same way as a string library, which works the same way as a window manager library. This often means that getting familiar and productive with new libraries is often much easier than in other languages. See More

Top Con

Symbols everywhere

Haskell allows users to define their own infix operators, even with their own precedence. The result is that some code is filled with foreign looking operators that are assumed to be special-case syntax. Even for programmers who know they're just functions, operators that change infix precedence can potentially break expectations of how an expression is evaluated, if not used with care. See More

Top Pro

Highly transferable concepts

Haskell's referential transparency, consistency, mathematics-oriented culture, and heavy amount of abstraction encourage problem solving at a very high level. The fact that this is all built upon little other than function application means that not only is the thought process, but even concrete solutions are very transferable to any other language. In fact, in Haskell, it's quite common for a solution to simply be written as an interpreter that can then generate code in some other language. Many other languages employ language-specific features, or work around a lack of features with heavy-handed design patterns that discourage abstraction, meaning that a lot of what is learned, and a lot of code that is needed to solve a particular problem just isn't very applicable to any other language's ecosystem. See More

Top Con

Package manager is unstable & lacking features

Cabal (There are other choices but this is the most popular) can not uninstall a package. Also working at a few locations it is difficult to have the same environment for each one be the same. See More

Top Pro

Referentially transparent

Haskell's Purely Functional approach means that code is referentially transparent. This means that to read a function, one only needs to know its arguments. Code works the same way that expressions work in Algebra class. There's no need to read the whole source code to determine if there's some subtle reference to some mutable state, and no worries about someone writing a "getter" that also mutates the object it's called on. Functions are all directly testable in the REPL, and there's no need to remember to call methods in a certain order to properly initialize an object. No breakage of encapsulation, and no leaky abstractions. See More

Top Con

You need some time to start seeing results

Haskell's static typing, while helpful when building a project, can be positively frustrating for beginners. Quick feedback for errors means delaying the dopamine hit of code actually running. While in some languages, a beginner's first experience may be their code printing "Hello World" and then crashing, in Haskell, similar code would more likely be met with an incomprehensible type error. See More

Top Pro

Very few language constructs

The base language relies primarily on function application, with a very small amount of special-case syntax. Once you know the rules for function application, you know most of the language. See More

Top Con

Lazily Evaluated

Haskell's lazy evaluation implies a level of indirection - you're not passing a value, you're passing a thunk. This is often difficult to grasp not just for beginners, but for experienced programmers coming from strictly evaluated languages. This also means that, since for many, strict evaluation is their first instinct, initial expectations of a function's performance and complexity are often broken. See More

Top Pro

Hand-writeable concise syntax

Conciseness of Haskell lets us to write the expression on the whiteboard or paper and discuss with others easily. This is a strong benefit to learn FP over other languages. See More

Top Con

You have to learn more than just FP

Haskell is not only a functional language but also a lazy, and statically typed one. Not only that but it's almost necessary to learn about monads before you can do anything useful. See More

Top Pro

Functions curry automatically

Every function that expects more than one arguments is basically a function that returns a partially applied function. This is well-suited to function composition, elegance, and concision. See More

Top Con

Documentation for most packages is short and lacking

A few Haskell packages are well documented but this is the exception, not the rule. Most of the time a list of function signatures is what passes for documentation. See More

Top Pro

Easy syntax for people with a STEM degree

Since the basic syntax is very similar to mathematics, Haskell syntax should be easy for people who have taken higher math courses since they would be used to the symbols used in maths. See More

Top Con

Too academic, hard to find "real world" code examples

Top Pro

Easy to read

Haskell is a very terse language, particularly due to its type inference. This means there's nothing to distract from the intent of the code, making it very readable. This is in sharp contrast to languages like Java, where skimming code requires learning which details can be ignored. Haskell's terseness also lends itself to very clear inline examples in textbooks, and makes it a pleasure to read through code even on a cellphone screen. See More

Top Con

Curried type signatures obfuscate what were the in and out types originally

Top Pro

Quick feedback

It's often said that, in Haskell, if it compiles, it works. This short feedback loop can speed up learning process, by making it clear exactly when and where mistakes are made. See More

Top Pro

Popular in teaching

Haskell is really popular in universities and academia as a tool to teach programming. A lot of books for people who don't know programming are written around Haskell. This means that there are a lot of resources for beginners in programming with which to learn Haskell and functional programming concepts. See More

Top Pro

Powerful Categorical Abstractions

Makes categorical higher order abstractions easy to use and natural to the language See More

See All

20 Other Options Considered

Clojure

Top Pro

Immutability is the default

Clojure programmers are highly encouraged to use immutable data in their code. Therefore, most data will be immutable by default. State change is handled by functions (for transformations) and atoms (an abstraction that encapsulates the idea of some entity having an identity). See More

Top Con

Confusing error messages

Clojure's error messages more often than not are very confusing. They usually involve stack traces that do not thoroughly explain where the error was caused or what caused it. See More

Specs

Site:www.clojure.org

Current stable version:1.9

Price:Free, Open Source

GZipped size:3.7Mb, requires JAVA

Top Pro

Minimal syntax

Being a LISP, programs are simple: they're just functions and data. That it doesn't get bogged down with syntax or the loftier FP concepts like monads makes it one of most approachable functional languages for beginners. See More

Top Con

Tied to the JVM and it's limitations.

Some language constructs were obviously created as workarounds for JVM limitations. This makes the language much less elegant than it could have been. Also, the JVM has a very cumbersome FFI. See More

Top Pro

Good for writing concurrent programs

Since Clojure is designed for concurrency, it offers things like Software Transaction Memory, functional programming without side-effects and immutable data structures right out of the box. This means that the development team can focus their energies on developing features instead of concurrency details. See More

Top Con

Syntax can be alien / jarring for those used to other Lisps

Perhaps some may consider this attribute an advantage, but I do not. Clojure does not attempt to maintain significant compatibility with other Lisps. So, if you already know a Lisp or are used to the way Lisp works in general, you'll probably be confused if you take a look at Clojure. See these resources for more details on this subject: https://clojure.org/reference/lisps http://stackoverflow.com/q/6008313/2636454 http://gilesbowkett.blogspot.com/2015/01/one-major-difference-between-clojure.html http://softwareengineering.stackexchange.com/q/153128/166211 See More

Top Pro

Huge ecosystem of libraries to work with

There's a very large ecosystem of high-quality Clojure libraries which developers can use. One example is Incanter. It's a great data analytics library and a very powerful tool for dealing with matrices, datasets and csv files. See More

Top Pro

Tries to solve problems as simply as possible

Simplicity is one of the pillars on which Clojure is built. Clojure tries to solve many problems in software development as simply as possible. Instead of building complex interfaces, objects or factories, it uses immutability and simple data structures. See More

Top Pro

Dynamic language

A superb data processing language. While rich type and specification systems are available they are optional. See More

Top Pro

Cross platform

Clojure compiles to JVM bytecode and runs inside the JVM. This means that applications written in Clojure are cross-platform out of the box. See More

Top Pro

Rich Hickey

The creator is so awesome, he's a feature. Just look up his talks and see why. See More

Top Pro

Extensible

Clojure has an elegant macro system which enables language additions, Domain-specific languages (DSLs), to be created much easier than most other languages (with the exception of Racket, perhaps). See More

Top Pro

Great tool used in automating, configuring and managing dependencies available

Leiningen is a very useful tool for Clojure developers. It helps wiht automation, configuration and dependency management. It's basically a must for every Clojure project. See More

Top Pro

Game is available with which you can learn Clojure

Nightmod is a tool used to make "live-moddable" games. It displays the game's code while you are playing and allows you to inject new code using Clojure. This can be a fun and useful experience for people trying to learn Clojure. See More

Top Pro

No C/Java syntax

Refreshing, BTW! See More

See All

Elixir

Top Pro

Great documentation

Elixir's documentation is very good. It covers everything and always helps solving any problem you may have. It's also always available from the terminal. See More

Top Con

Some design choices may seem strange

Some design choices could have been a little more appealing, for example: using "do...end" comes natural in Ruby for blocks but Elixir uses them for everything and it looks pretty weird: Enum.map [1, 2, 3], fn(x) -> x * 2 end or receive do {:hello, msg} -> msg {:world, msg} -> "won't match" end See More

Specs

Site:https://elixir-lang.org

Current stable version:1.6

Price:Open source (Free)

GZipped size:3.61 MB (without required Erlang VM)

Top Pro

Great for concurrency

Leverages the existing Erlang BEAM VM See More

Top Pro

Great getting started tutorials

The tutorials are very clear and concise (even for a person not used to functional programming). Plus they are also very mobile friendly. See More

Top Pro

Syntax is similar to Ruby, making it familiar for people used to OOP

All of the benefits of Erlang; without as steep a learning curve of prolog based syntax. Elixir is heavily inspired by Ruby's syntax which many people love. See More

Top Pro

Powerful metaprogramming

Write code that writes code with Elixir macros. Macros make metaprogramming possible and define the language itself. See More

Top Pro

Easy to download libraries

Comes with built in build tool called "mix". This will automatically download libraries and put them in the scope of the application when you add them to the "deps" function and run mix deps.get See More

Top Pro

Full access to Erlang functions

You can call Erlang functions directly without any overhead: https://elixir-lang.org/getting-started/erlang-libraries.html See More

Top Pro

Types don't get in the way

See All

Scheme

Top Pro

Simple syntax

Scheme syntax is extremely regular and easy to pick up. A formal specification of the syntax fits onto just a few pages; it can be introduced informally in a paragraph or two. Students are not distracted by remembering how to write if statements or loops or even operator precedence because every syntactic follows the same pattern. Ultimately, everything looks something like this: (func a b c) This includes not only user-defined functions but even control flow: (if cond then-clause else-clause) or even primitive operations like define and set: (define foo 10) (set! foo 11) This means that nothing really has special syntactic treatment in the language. There are essentially no weird edge-cases to memorize, and different concepts are given a more equal weight in the language. (Unlike Algol-like languages which tend to given undue weight to loops and assignment statements, for example.) See More

Top Con

Fragmented ecosystem

Scheme is an IEEE standard, not an implementation. Unfortunately, the standard is too minimal and practical implementations have diverged--they had to expand on the standard to get anything done, but did so in incompatible ways. The later de facto standard R6RS tried to correct this, but lost Scheme's minimalist elegance in the process. The newer R7RS standard takes the best of both worlds with an elegant minimalist core and a practical standard library. See More

Top Pro

Great, well known textbooks available

There is a set of very strong textbooks introducing CS and programming using Scheme. These books are available for free online. The most famous example--and one of the most famous CS books full stop--is Structure and Interpretation of Computer Programs usually known as SICP. This book introduces fundamental ideas in computer science and covers an incredible amount of material quickly and clearly without requiring any prior knowledge. However, some people find SICP a bit challenging as a first text. Happily, there are other more introductory texts as well. Simply Scheme is a book designed to be read before SICP, easing beginners into the language as well as CS and programming in general. How to Design Programs is another text used in introductory college courses. See More

Top Con

Not purely functional

Scheme is a multi-paradigm language including metaprogramming and procedural elements alongside functional elements. As such it will not give a clear impression of a purely functional language. See More

Top Pro

Great at teaching fundamental programming ideas

Scheme teaches the important, fundamental ideas immediately without the distraction of unnecessary syntax or language features. See More

Top Pro

No Magic - it's clear how everything works

Scheme has far less built into the language itself, helping students see that things like OOP are not magical: they are just patterns for organizing code. Everything in Scheme is built up from a very small set of primitives which compose in a natural and intuitive fashion. Having a language that does not accord many things special status helps keep students open minded. This will help students later go between different languages and paradigms from procedural to object-oriented to functional. See More

Top Pro

Many different implementations for different domains

There are around 30 different implementations of the most recent Scheme standard (R7RS), optimized for different domains - from embedded systems over native compilation, desktop programs, web services and the JVM up to targeting Javascript in Browsers. See More

Top Pro

Multiparadigm

Unlike most languages, Scheme actually accords both functional programming and imperative programming roughly equal status. Many other languages like Python and Java are staunchly imperative while SML and Haskell are primarily functional; Scheme is a nice middle ground. Additionally, since Scheme syntax is extremely flexible, it can easily be re-purposed for teaching non-deterministic and logic programming. There is no need to learn a new language like Prolog when the same ideas can easily be expressed with Scheme syntax. This gives students a good perspective on different ways to think about and organize programs, which makes it much easier to move forward to other languages and technologies. See More

Top Pro

Great, well known textbooks

There is a set of very strong textbooks introducing CS and programming using Scheme. These books are available for free online. The most famous example--and one of the most famous CS books --is Structure and Interpretation of Computer Programs usually known as SICP. This book introduces fundamental ideas in computer science and covers an incredible amount of material quickly and clearly without requiring any prior knowledge. However, some people find SICP a bit challenging as a first text. Happily, there are other more introductory texts as well. Simply Scheme is a book designed to be read before SICP, easing beginners into the language as well as CS and programming in general. How to Design Programs is another text used in introductory college courses. See More

See All

Racket

Top Pro

Racket was designed to teach functional programming from the start

Racket is based on Scheme (LISP Family) and is very similar to Clojure. So there are a ton of (). The reason it is easier to learn is that it is not trying to be "Pure" if there is even such a thing in terms of Functional Programming. The great thing about Racket is it has everything included. You get DrRacket for developing programs. You want to add a picture to your software you can insert pictures. If you want to add libraries just open the package manager. The Syntax is an opinion but it really does feel easier to see what is happening since everything is in brackets) Racket is a really a Programming Language for making Programming Languages. So there are smaller syntax Racket called Student Racket which makes things easier to pick up. See More

Specs

Site:racket-lang.org

Current stable version:6.11

Price:Free

OS:Linux, Windows, OSX

See All Specs

Top Pro

Realm of Racket is an excellent entry-level guidebook

Realm of Racket teaches the big-bang approach for managing world state. It does so by walking the reader through the development of small games. There are few guidebooks that are as useful and entertaining. See More

Top Pro

Free resources to Learn

Includes several free online books and great documentation. See More

Top Pro

Easily embeddable

Racket is famously embedded in the game engine underlying Naughty Dog's Uncharted and The Last of Us games, because it proved to be so easy to embed. See More

Top Pro

Syntax fits to functional programming

Although syntax is different from that of mainstream languages, S-expressions are a perfect match to functional programming. See More

Top Pro

Active community

Racket has an active community of users/developers that makes it easy to get help when needed. See More

Top Pro

Great RPEL IDEA included Dr. Racket

See All

F#

Top Pro

Concise syntax

F#'s syntax tends to be terse while remaining very readable and easy to understand without being a chore to write. See More

Top Con

Has no ad-hoc polymorphism (á la Type Classes)

You have generics, you have interfaces, you have inheritance, you have a lot of things at your disposal but you don't have Type Clases. They can be emulated using some clever constructs but there's nothing like having the real thing. See More

Ernesto Barros's Experience

It looks so much like Elm and it works everywhere. With great community and very friendly Editor! If you like Elm then you ought to look at F# :-) They are so good at explaining new ideas. You will always be on the frontline of adopting new technologies!! Which is a big + to me!! See More

Specs

Site:http://www.fsharp.org

Current stable version:4.1

License:Apache 2.0

IDE Support:Visual Studio, Code, Rider

Top Pro

Easier transition from other paradigms

Since F# is not a purely functional language, it lends itself to being more easily picked up by programmers that have experience with other paradigms. See More

Top Con

Not really cross platform

Though the community sites are touting F# can be cross platform through use of Mono, the reality is that it is more of a hack to replay on larger mono applications in production. See More

Top Pro

.NET Interoperability

Since F# runs on the Common Language Runtime or CLR, it has access to the entire .NET Framework, as well as libraries written in other .NET languages such as C#, VB.NET, and C++/CLI. See More

Top Pro

Multiplatform, it runs on .Net Core

Forget Xamarin and Mono. F# now runs on the multiplatform .Net Core! See More

Top Pro

Natively supported by Visual Studio

This is a .Net language natively supported by Visual Studio. Though it is not as tooled up as C# the support is still substantial. In particular, C# deployment scenarios can be enabled for it with small C# wrapper projects. Integration with Visual Studio provides: IntelliSense, debugging, projects an other features. See More

Top Pro

Allows writing predictable code

Like many other functional languages, F# takes a stance of immutability for most of its constructs (state, values etc...). There are several reasons why having immutable values is good. One of those is that the code you are writing becomes much more predictable and you don't have to worry about any side effects. See More

Top Pro

You can run F# in the browser

Thanks to a project like Fable, you can write and run your client app in F# and run it over JavaScript. It allows you to share code between your server and client. See More

Top Pro

Fall into the pit of success

F# directs you into a workflow where the right way is the path of least resistance. Coming from a C# background, its restrictions might feel arbitrary at first (e.g., what do you mean my code has to be in dependency order!? Arbitrary alphabetical or bust!), but you'll soon realize that your code is cohesive, concise and consistent in a way that it never was before - and you can compile and run with confidence! See More

Top Pro

F# is supported by Xamarin

Thanks to Xamarin, F# is a functional language that you can use to build for iOS, Android and Windows. See More

Top Pro

Type Providers

See All

OCaml

Top Pro

Encourages functional style

It steers you towards a functional style, but doesn't bother you with purity and "monads everywhere" like other languages, such as Haskell. See More

Top Con

Strong focus on *nix systems, lacking native support for MS Windows

Lacks native support for Windows systems. See More

PracticalDekla's Experience

pragmatic functional programming. See More

Specs

Site:http://ocaml.org

Current stable version:4.0.6

Price:Open source (Free)

License:LGPL version 2.1

See All Specs

Top Pro

Actively-developed functional programming language at the forefront of research

Functional programming is based on the lambda calculus. OCaml is in its functional parts almost pure lambda calculus, in a very practical manner: useful for many daily programming tasks. The acitve development makes improvements to the type system like generalized algebraic data types (GADT) or polymorphic variants, so when learning this language you get at once a down to earth usable compiler and advanced abstraction features. See More

AuthenticHlin's Experience

compiles to machine code, safe and productive See More

Top Pro

Sophisticated and easy-to-use package manager

OPAM is a package manager for OCaml, which is really easy to use, just like npm. It creates a .opam folder in home directory. The documentation is great as well, and you can switch between multiple versions of OCaml for each project. You can also package your project and publish it on OPAM repositories, even if the dependencies do not exists on OPAM. See More

Top Pro

One of the best for writing compilers

OCaml is compiled to native binary, so it's amazingly fast. Being a member of ML-family languages, it has expressive syntax for trees, and has great LLVM support. See More

Top Pro

Stable syntax

The syntax is consistent, some syntaxic sugar but at a reasonable level, so reading code of others isn't too much confusing. See More

Top Pro

Strong editor integration

The merlin editor tool provides all you need to develop OCaml in your favourite editor. See More

See All

Idris

Top Pro

Full dependent types

Idris not only has support for type classes, but is a fully dependently typed language, giving you the full power to statically verify your code. See More

Top Con

The language is still under development

Top Pro

Domain driven design and type driven development

Because of full dependent types in Idris, the programmer can focus more on modelling the domain with types and waste less time fixing common bugs that the type checker will catch. Dependent types help apply type driven development and a lot of code auto generation, making the compiler and type checker an ally in developing working software instead of just getting in the way. See More

Top Con

Different semantics from Haskell

Idris, while similar to Haskell, has strict semantics, which may cause some confusion if your backend is done in Haskell. If using Idris, it would make sense to do the backend in Idris as well, if not for the fact that Idris currently has fewer libraries available for web development than Haskell. See More

Top Con

Weaker type inference

As type inference is undecidable for dependently-typed languages, Idris cannot offer the full type inference that Haskell supports, and so more type annotations will be needed. See More

See All

Erlang

Top Pro

Battle proven

Erlang has been used in production for more than 20 years now. During that time it has proven itself over and over again that works great in both small startups and large-scale enterprise systems. Erlang has been used extensively by Ericsson themselves. For example, the AXD301 ATM, which is one of Ericsson's flagships is probably the largest Erlang project ever with more than 1.1 million lines of Erlang code. See More

Top Con

Strange syntax

Erlang's syntax may feel very strange to 99% of programmers who have never used it. This is because it does not share any similarities or common syntax definitions that are found in all the other languages that are used today. See More

Deuxis's Experience

To quote Evan Miller, "The good news about Erlang can be summed up at this: Erlang is the culmination of twenty-five years of correct design decisions in the language and platform. Whenever I've wondered about how something in Erlang works, I have never been disappointed in the answer. I almost always leave with the impression that the designers did the “right thing”. I suppose this is in contrast to Java, which does the pedantic thing, Perl, which does the kludgy thing, Ruby, which has two independent implementations of the wrong thing, and C, which doesn't do anything." See More

Specs

Site:https://www.erlang.org/

Top Pro

Built from the ground up with concurrency and distributed computing in mind

Erlang has strong roots with the telecom industry in which concurrent processes are normal. It's designed to be concurrent, to be used for distributed computing and to be scalable. See More

Top Con

Useful in only one niche

Erlang is not really a general purpose language. It has a very special and well-defined niche where it towers above everything else. It's specialized in scalability and in distributed applications. Which is not necessarily a bad thing per se, but it still lacks and falls behind other languages when it needs to do things outside it's niche. See More

Top Pro

Consistency across platforms

Erlang's processes run in a complete independent way from the OS (they aren't managed by the OS scheduler neither). This means that programs written in Erlang will run exactly the same way regardless of the operating system or platform. See More

Top Pro

Little overhead

Erlang's processes have very little overhead (about 500 bytes per process). This means that a huge amount of processes can be created, even on older machines. See More

Top Pro

Fault-tolerant

Fault tolerance means that a system has the property to continue operating even though one or more components have failed. For Erlang systems, this means that the system is kept running even if for example a user has to drop a phone call rather than forcing everyone else to do so. In order to achieve this, Erlang's VM gives you: Knowledge of when a process died and why that happened The ability to force processes to die together if they depend on each other and if one of them has a fault. A logger that logs every uncaught exception Nodes that can be monitored so that you find out when they go down The ability to restart failed processes (or groups of them) See More

Top Pro

Great for writing distributed applications

Erlang is made to be parallel and distributed. Because it's very easy to write code that uses multiple processor cores, it's also very easy to write applications that span multiple servers. See More

Top Pro

Upgrade code without stopping the system

In a real-time system it may not be possible to stop the system in order to implement code upgrades. For these cases Erlang gives you dynamic code upgrade support for free when using OTP. The mechanism is very easy to understand and works as follows: Start the app Edit the code Recompile That's all that is needed, the app updates with the new code while it's still running and tests are run automatically. See More

Top Pro

Designed to be intuitive

Erlang's eccentric syntax and features were created to be natural for humans, not just for programmers used to the C style. Functions (or rather, all blocks/statements) are structured like sentences, with commas separating the instructions, semicolons separating overloads of the same function and a period marking the end. Dynamic but strong typing means that types are no concern but there are no weird implicit conversions. Destructuring operations are the standard. The ultra-light and easy to manage processes communicating via messages are basically the dream of anyone wanting to touch concurrency. There is even an entire section of the language dedicated to parsing and constructing binary blobs in an intuitive way. See More

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Scala

Top Pro

Compiles to JVM bytecode, making applications written in Scala cross-platform

Aside from Java itself, Scala is by far the most popular of the many JVM languages. If you're developing for Android, or a similar JVM-only platform, or otherwise need out-of-the-box cross-platform compatibility, but the performance of a compiled language, Scala is the way to go. See More

Top Con

Limited type inference

Compared to other languages with type inference, such as Haskell, Scala's implementation is quite limited See More

Specs

Site:scala-lang.org

Current stable version:2.12.6

Price:Open Source (Free)

Top Pro

Supports both Functional and OOP paradigms

Scala supports both Functional and Object Oriented styles of programming. Beginners can learn both paradigms without having to learn a new language, and experts can switch between the two according to what best suits their needs at the time. See More

Top Con

Can be intimidating for beginners

Scala is an industrial language. It brings functional programming to the JVM, but not with a "start small and grow the language" perspective, but rather a very powerful language for professional programmers. See More

Top Pro

Great for concurrency

The immutable values make it perfect for working with concurrency. See More

Top Con

All the object-oriented constructs distract from learning functional programming concepts

It's not a "functional only" or even a "functional first" language. It 's very heavily object-oriented and all the functional concepts are implemented via OOP constructs or have to be implemented by the programming via those OOP construct (patterns). This makes it way more confusing to learn the functional programming concepts. See More

Top Pro

Powerful static type system

It make easy to create complex abstractions and statically guarantee the safety of your program See More

Top Con

Static type system inherits cruft from Java

The type system is too complicated yet still less powerful than Haskell's. See More

Top Pro

Offers type inference

Scala offers type inference, which, while giving the same safety as Java's type system, allows programmers to focus on the code itself, rather than on updating type annotations. See More

Top Con

Way too complex for beginners

Even for seasoned programmers it's a difficult language. See More

Top Pro

Great REPL

It makes it easy to practice or test code. See More

See All

Python

Top Con

Not designed for functional programming

Bare minimal list functions and no tail recursions. Biggest hangup is the imperative syntax which makes it difficult to make it have weak expressions. See More

Top Pro

Easy to use

Specs

Current stable version:3.7.0 and 2.7.15

GZipped size:22.5MB

Language type:Interpreted

Top Con

Not a fully functional language

Python is missing several features that make it fully functional, and has several design issues that make pure-functional programming a chore at best. The biggest of these is the limitations of lambdas and dysfunctional closure scoping. See More

Top Pro

Applications or web-based

Can be used in both OS and web-based environments very well. See More

Top Con

Slightly slower

When microseconds are involved and very high data throughput, python can respond slower than a base C/C++ application. But not very much. See More

Top Pro

Can use both functional and object oriented paradigms

Python is not too functional and not too object oriented, so you can freely choose any paradigm when you see fit. See More

Top Con

Inelegant and messy language design

The first impression given by well-chosen Python sample code is quite attractive. However, very soon a lack of unifying philosophy / theory behind the language starts to show more and more. This includes issues with OOP such as lack of consistency in the use of object methods vs. functions (e.g., is it x.sort() or sorted(x), or both for lists?), made worse by too many functions in global name space. Method names via mangling and the init(self) look and feel like features just bolted on an existing simpler language. See More

Top Pro

Easy to get started

On top of the wealth of tutorials and documentation, and the fact that it ships with a sizeable standard library, Python also ships with both an IDE (Integrated Development Environment: A graphical environment for editing running and debugging your code); as well as a text-based live interpreter. Both help users to get started trying out code immediately, and give users immediate feedback that aids learning. See More

Top Con

Multiparadigm

While Python has powerful enough features to do functional programming, this is not required or even Pythonic (i.e. idiomatic for Python code). Unless you have a text or course specifically designed to teach the functional style in Python, learning Python really won't teach it. See More

Top Pro

Fast

Top Con

Unflexible userbase

You will be expected to rigidly stick to the coding practices and to do everything by-the-numbers. See More

Top Pro

Powerful full functional language

Top Con

Limited support for functional programming

While Python imports some very useful and elegant bits and pieces from FP (such as list comprehensions, higher-order functions such as map and filter), the language's support for FP falls short of the expectations raised by included features. For example, no tail call optimisation or proper lambdas. Referential transparency can be destroyed in unexpected ways even when it seems to be guaranteed. Function composition is not built into the core language. Etc. See More

Top Con

Significant whitespace

While proper formatting is essential for any programmer, beginners often have trouble understanding the need and lack the discipline to do it. Add to that all those editors that randomly convert N spaces (usually 8) to tabs and you get an instant disaster. See More

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Kotlin

Top Pro

Great tooling support

Since Kotlin is made by Jetbrains (the developers of IntelliJ IDEA) so it stands to reason that the IntelliJ support for Kotlin is also great. Besides that, Kotlin also works well with existing Java tools such as Eclipse, Maven, Gradle, Android Studio, etc... See More

Top Con

May be hard for programmers already used to imperative style to learn functional programming from Kotlin

Since Kotlin does not enforce any particular paradigms and is not purely functional, it can be pretty easy to fall back to imperative programming habits if a programmer comes from an imperative background. See More

Specs

Site:http://kotlinlang.org

Current stable version:1.2

Price:Free, Open Source

Top Pro

Easy adoption for existing Java programmers

Kotlin runs on the JVM and Java interoperability has been one of the main objectives since the language was born. It runs everywhere Java does; web servers, mobile devices (Android), and desktop applications. It also works with all the major tools in the Java ecosystem like Eclipse, IntelliJ, Maven, Ant, Gradle, Spring Boot, etc. All of this makes adoption extremely easy even for existing Java projects. On top of this there's also ensured Type safety and less boilerplate code needed. See More

Top Con

The need for Java interoperability has forced some limitations

The need to make Kotlin interoperable with Java has caused some unintuitive limitations to the language design. See More

Top Pro

Easy to learn if you have prior programming experience

Kotlin's syntax is extremely easy to understand. The language can be picked up in a few hours just by reading the language reference. See More

Top Pro

No runtime overhead

The standard library is relatively small and tight. It mostly consists of focused extensions of the Java standard library and as such adds no additional runtime overhead to existing Java projects. See More

Top Pro

Officially supported for Android development

Starting with version 3.0 of Android Studio, Kotlin support will be built-in. This means that it's now easier than ever to use Kotlin for existing Android projects or even start writing Android apps only with Kotlin from scratch. This also means that Kotlin and Kotlin plugins for Android Studio will be fully supported in the future and their likelihood of being abandoned is quite small since Google is fully embracing the language for their Android ecosystem (alongside Java and C++). See More

Top Pro

Low-risk adoption for existing Java codebases

Since it has such a good interoperability with Java, Java libraries, and Java tools. It can be adopted for an existing Java codebase at little to no cost. The codebase can be converted from Java to Kotlin little by little without ever disrupting the functionality of the application itself. See More

Top Pro

Does not impose a particular philosophy of programming

It's not overly OOP like Java and it does not enforce strict functional paradigms either. See More

Top Pro

Is built to solve industrial problems

Kotlin has been designed and built by developers who have an industrial background and not an academic one. As such, it tries to solve issues mostly found in industrial settings. For example, the Kotlin type system helps developers avoid null pointer exceptions. Reasearch languages usually do not have null at all, but APIs and large codebases usually need null. See More

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Standard ML

Top Pro

Powerful module system

The module system that Standard ML uses gives the programmer the power to define custom data types whose internal implementation is invisible to other programmers using the module. See More

Top Con

Not very popular outside academia

SML is mostly used in academia and doesn't have many uses in industry. While it's a good language for learning functional programming concepts, the language itself won't be very useful. See More

Top Pro

Implementing laziness is trivial

Since mutability is only confined to a special type of reference cells, implementing laziness in SML can be done in only 20 lines of code. See More

Top Pro

Enforces distinction between data and computations

Since it uses strict evaluation, it enforces distinction between data and computations which in turn enables you to use induction on algebraic data types as a reasoning principle. See More

Top Pro

Great exception system

Secret messages can be sent across distant parts of a program without possibility of being intercepted by unintended recipients in the middle. See More

See All

J

Top Con

Syntax is pure madness

quicksort=: (($:@(<#[), (=#[), $:@(>#[)) ({~ ?@#)) ^: (1<#) See More

Top Pro

Every function is an operator

3 classes of operators (verbs, adverbs, and conjunctions) with verbs the most basic function that take either 1 or 2 (infix) parameters. Operators allow function composition with a minimum of parentheses. See More

Top Pro

Simpler Imperative language constructs as failback to functional programming

J also supports multiline functional definitions similar to BASIC/Pascal. Including error handling. See More

Top Pro

Compiled language speed from interpreted language.

Each built in operator is a C/asm function, and special code further optimizes some operator combinations. Result is optimized C speed from quick parsing. Array orientation parses and compiles a function once, and applies it to all array items. See More

Top Pro

25 year old language, with core unchanged in last 10 years

Still actively developed, but most recent changes have been in libraries and IDE and platform support. Language is considered "perfected"... though not quite. See More

Top Pro

Language reference has simple one page index

Complete core programming functional tools allow writting programs and libraries without imports. See More

Top Pro

No operator precedence rules

(... within each of the 3 operator classes) makes reading code easier. Very simple parsing rules. See More

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Groovy

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