README.md

Miscellaneous

There are several minor differences to Haskell and other things that we won't cover in detail but are still worth noting:

The type hierarchy is more granular than Haskell's.
Typeclasses with a superclass use <= instead of Haskell's => to express dependencies in class (Eq a) <= Ord a where.
The compiler performs tail-call elimination.
Type variables must be explicitly declared with forall.
No syntactic sugar for the Array type (but array values have it).
No syntactic sugar for list comprehensions -- use do notation instead.
() in Haskell is Unit in PureScript.
head and similar functions are total (return Maybes) by default.
The functor map function is simply called map instead of fmap as in Haskell.
Operators must be defined with parentheses: ($) f x = f x (not f $ x = f x).
Function composition is <<< rather than . to avoid syntactic ambiguity with record proprty access and name qualification. (<<< is actually more general than ..)
PureScript does not support language extensions, but support (approximately) the following Haskell-equivalents by default:
- EmptyDataDecls
- ExplicitForAll
- FlexibleContexts
- FlexibleInstances
- MultiParameterTypeClasses
- PartialTypeSignatures
- RankNTypes
- ScopedTypeVariables

Most of the above are from the PureScript Wiki's Differences from Haskell page.