When comparing OCaml vs Erlang, the Slant community recommends OCaml for most people. In the question“What are the best (productivity-enhancing, well-designed, and concise, rather than just popular or time-tested) programming languages?” OCaml is ranked 14th while Erlang is ranked 40th. The most important reason people chose OCaml is:
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.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
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.
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.
Pro No windows!
Strong focus on *nix systems, lacking native support for MS Windows
Lacks native support for Windows systems.
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.
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.
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.
Pro Strong editor integration
The merlin
editor tool provides all you need to develop OCaml in your favourite editor.
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.
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)
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.
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.
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.
Pro Light processes
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.
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.
Cons
Con Strong focus on *nix systems, lacking native support for MS Windows
Lacks native support for Windows systems.
Con Eccentric 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.
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.