When comparing Fay vs Utrecht Haskell Compiler, the Slant community recommends Fay for most people. In the question“What are the best solutions to "The JavaScript Problem"?” Fay is ranked 11th while Utrecht Haskell Compiler is ranked 18th. The most important reason people chose Fay is:
Fay produces smaller output than pure Haskell compilers such as GHCJS; It does not need to include the whole Haskell runtime, as it drops support for features such as multi-threading, giving it fewer dependencies.
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Pros
Pro Small output
Fay produces smaller output than pure Haskell compilers such as GHCJS; It does not need to include the whole Haskell runtime, as it drops support for features such as multi-threading, giving it fewer dependencies.
Pro Simple, flexible, hackable FFI
As with UHC, the FFI to Javascript works with printf-style format:
max = ffi "Math.round(%1,%2)"
This can simplify code needed to make calls to methods on objects, in contrast to e.g., Purescript's FFI, which requires that methods be wrapped in Javascript. Similarly to UHC, Fay also supports the use of %*
, for javascript functions with arbitrary numbers of parameters, such as concat
, though they must expose an explicit number of parameters to Fay.
Pro Easy to set up, with packages available on Cabal
Fay is available on Cabal, as are Fay packages, so getting up and running is as simple as typing 'cabal install'. Happstack, Snap, and Yesod packages are available on Hackage, as are bindings for JQuery and Backbone.
Pro Subset of Haskell - nothing new to learn
Since Fay is a subset of Haskell - Lazy, statically typed, and pure by default. There's no new syntax to learn, and no surprises when it comes to the semantics of your code. This extends into function names as well - Fay programmers can use familiar functions such as putStrLn
to output to the console, rather than Javascript-specific versions.
Pro It's just Haskell
No need to learn any new semantics, it's just a switch to a different compiler.
Pro Flexible FFI
UHC uses a printf-like syntax for its FFI, which is flexible enough to minimize the need for wrapper functions, when, e.g., calling methods on objects. It also supports %*
, for working with functions that take arbitrary parameters, such as concat
.
UHC also has support for wrapper imports and dynamic imports, for passing Haskell functions as callbacks to Javascript, or dealing with curried Javascript functions, respectively.
Cons
Con No typeclasses
This can cause some overhead.
Con No support for Language Extensions
No support for things like Arrow Syntax - this is particularly a disadvantage when compared to options like Elm (which was designed around good syntax for Arrowized FRP), if you're looking to do Functional Reactive front-end development.
