regex-posix. This library is an official component of the Haskell Platform, and is part of the "batteries included" concept. The following commentary is based primarily on its Haddock documentation; links are provided.
regex-posixexports six modules:
Text.Regex.Posix— directly exports only one symbol, a constant. Also re-exports instances from the remainder fo the package.
Text.Regex.Posix.ByteString— Exports four data types (including newtypes), three type synonyms, nine constants, and three functions, all in the IO monad; acocrding to the documentation, it also provides orphan instances for two type classes,
RegexMaker, provided by the
Text.Regex.Posix.ByteString.Lazy— Exports exactly the same API as the previous package, but with different orphan instances.
Text.Regex.Posix.Sequence— Exports exactly the same API as the previous package, but with different orphan instances.
Text.Regex.Posix.String— Exports exactly the same API as the previous package, but with different orphan instances.
Text.Regex.Posix.Wrap— Exports four data types (including newtypes), three type synonyms, 21 constants, five functions in the IO monad, one constrained polymorphic function returning a simple value, and one constrained polymorphic function returning a value in an arbitrary monad.
for different types
regexec :: Regex -> string -> IO (Either WrapError (Maybe (string, string, string, [string])))
string. However, in fact, these functions are not combinators, for the following reasons:
- The argument is of type
string; the result is not. The result strings are in fact nested in a mult-result return wrapped inside three monads.
- All three monads involved are exception monads, meaning that attempting to un-pack the result of a
regexeccall may fail to produce any
stringvalues at all.
stringvalues returned, if any, are shorter and simpler than the input.
regex-basepackage, which these reviews will be reaching in a few days, we defer consideration to the review of that package. In the meantime, we can conclude that there is no evidence that this library is written in a combinatorial, rather than imperative, style.