PureScript vs Pony
When comparing PureScript vs Pony, the Slant community recommends Pony 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?” Pony is ranked 22nd while PureScript is ranked 45th. The most important reason people chose Pony is:
The unique type system allows the compiler to automatically schedule actors on threads, giving you reliable concurrency for free.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Higher kinded types
Has Typeclasses and RankNTypes

Pro High performance FFI code
The Eff monad, which is used for FFI code, optimizes out calls to bind, and supports tail call optimization, resulting in clean, efficient Javascript. The psc compiler also specifically recognizes the ST monad, and transforms scoped variables into mutable Javascript variables, for even more efficient code.
Pro Type safety
Compiling should be your first unit test. A tight type system (static and hopefully strong) will catch many logic errors that are often difficult to spot through debugging. In languages like PureScript, if it compiles, it often runs properly.
Pro Pure functional language
You cannot have side effects, unless a function is explicitly defined as so.
Pro Modules can be compiled to CommonJS
Modules compiled to CommonJS can be included with 'require', making it incredibly simple to call Purescript code from Javascript.
Pro Has row polymorphism and extensible effects
Pro FFI
FFI system is quite good and easy to use. You can import functions curried or not curried. Records and arrays use native JS objects and arrays.
Pro Thorough documentation
The Purescript website has fairly thorough documentation for all of the language's features, and the Purescript blog contains several examples of practical usage.
Pro Awesome web frameworks
Thermite (React)
Halogen (VDOM, similar to ELM)
And hit these up with Signals, Isolated/(Managed?) Components, powerful functions and FFI
Pro Concurrency model based on actors
The unique type system allows the compiler to automatically schedule actors on threads, giving you reliable concurrency for free.
Pro Reliable
Because of its capabilities secure type system, provided you don't use the C FFI, references will never be stale, race conditions are effectively impossible, deadlocks don't happen because locks and mutexes are never needed, and processes never crash because all exceptions must be handled. (Barring compiler bugs or external memory corruption, of course.) Pony programs can still lock up due to infinite loops, like any Turing-complete language.
Pro High performance
Compiles to native code, and features an intelligent garbage collector that takes advantage of the actor architecture to get essentially free garbage collection.
Pro Trivially simple C FFI
Calling low-level C functions is as simple as use "lib:clibrary"
and @c_function_name[return_type](parameter:type)
. Linking C to Pony libraries is just as easy, as the Pony compiler will generate appropriate header files.
Cons
Con Lots of dependencies needed to get started
Purescript is written in Haskell, but meant to be used with Node.js. As a result, to get started , users must install ghc, cabal, node.js, grunt, and bower. Purescript also has its own compiler, and different semantics form Haskell, and so even after installing, there's still some overhead to getting productive with Purescript.
Con Lack of good IDE/tooling support
Con Documentation not updated
Con Ecosystem not stable
Con Restrictive FFI
Functions exported are all curried, and must be called as such from Javascript. The FFI syntax for importing Javascript functions, while slightly simpler and more readable than UHC/Fay's, means that calls to methods on objects must be wrapped to pass the object explicitly as a parameter.
Con Slow compilation
On large project, for example Halogen
Con All exceptions must be caught
The compiler enforces this, so code is littered with try
s.
Con Limited documentation
As Pony is such a new language, documentation is relatively light, and tutorials are few and far-between.
Con Few libraries
Con Garbage collector can't run until you yield
A long-running behavior can leak memory because the garbage collector has no chance to run.
Con Limited tooling
There's no IDE. Debuggers are fairly basic. Pony is too young to have much of an ecosystem.
Con Divide by zero is allowed
And instead of some sensible result like NaN or Inf, the answer is zero! Most languages would just raise an exception (and Pony used to do this), but since the compiler enforces the rule that "all exceptions must be caught" the proliferation of try
s was determined to be too burdensome on the programmer. This makes the whole design of the exception system questionable.
Con Unstable API
Pony is not ready for production. It has yet to release version 1.0, and there are frequent breaking changes.
Con Difficult learning curve
The type system uses a capabilities-oriented approach to reference semantics, which can be difficult to wrap your head around at first. The lack of more common object-oriented features and the preference for simplicity over familiarity can make it difficult for new users to model their program design.
