pipes-parse-3.0.8: Parsing infrastructure for the pipes ecosystem

Pipes.Parse

Description

Element-agnostic parsing utilities for pipes

See Pipes.Parse.Tutorial for an extended tutorial

Synopsis

# Parsing

pipes-parse handles end-of-input and pushback by storing a Producer in a StateT layer.

Connect Parsers to Producers using either runStateT, evalStateT, or execStateT:

runStateT  :: Parser a m r -> Producer a m x -> m (r, Producer a m x)
evalStateT :: Parser a m r -> Producer a m x -> m  r
execStateT :: Parser a m r -> Producer a m x -> m    (Producer a m x)
^^^^^^^^^^^^^^
Leftovers

type Parser a m r = forall x. StateT (Producer a m x) m r Source #

A Parser is an action that reads from and writes to a stored Producer

draw :: Monad m => Parser a m (Maybe a) Source #

Draw one element from the underlying Producer, returning Nothing if the Producer is empty

skip :: Monad m => Parser a m Bool Source #

Skip one element from the underlying Producer, returning True if successful or False if the Producer is empty

skip = fmap isJust draw

drawAll :: Monad m => Parser a m [a] Source #

Draw all elements from the underlying Producer

Note that drawAll is not an idiomatic use of pipes-parse, but I provide it for simple testing purposes. Idiomatic pipes-parse style consumes the elements immediately as they are generated instead of loading all elements into memory. For example, you can use foldAll or foldAllM for this purpose.

skipAll :: Monad m => Parser a m () Source #

Drain all elements from the underlying Producer

unDraw :: Monad m => a -> Parser a m () Source #

Push back an element onto the underlying Producer

peek :: Monad m => Parser a m (Maybe a) Source #

peek checks the first element of the stream, but uses unDraw to push the element back so that it is available for the next draw command.

peek = do
x <- draw
case x of
Nothing -> return ()
Just a  -> unDraw a
return x

isEndOfInput :: Monad m => Parser a m Bool Source #

Check if the underlying Producer is empty

isEndOfInput = fmap isNothing peek

Arguments

 :: Monad m => (x -> a -> x) Step function -> x Initial accumulator -> (x -> b) Extraction function -> Parser a m b

Fold all input values

Control.Foldl.purely foldAll :: Monad m => Fold a b -> Parser a m b

Arguments

 :: Monad m => (x -> a -> m x) Step function -> m x Initial accumulator -> (x -> m b) Extraction function -> Parser a m b

Control.Foldl.impurely foldAllM :: Monad m => FoldM a m b -> Parser a m b

# Parsing Lenses

Connect lenses to Producers using (^.) or view:

(^.) :: Producer a m x
-> Lens' (Producer a m x) (Producer b m y)
-> Producer b m y

Connect lenses to Parsers using zoom:

zoom :: Lens' (Producer a m x) (Producer b m y)
-> Parser b m r
-> Parser a m r

Connect lenses to each other using (.) (i.e. function composition):

(.) :: Lens' (Producer a m x) (Producer b m y)
-> Lens' (Producer b m y) (Producer c m z)
-> Lens' (Producer a m y) (Producer c m z)

span :: Monad m => (a -> Bool) -> Lens' (Producer a m x) (Producer a m (Producer a m x)) Source #

span is an improper lens that splits the Producer into two Producers, where the outer Producer is the longest consecutive group of elements that satisfy the predicate

splitAt :: Monad m => Int -> Lens' (Producer a m x) (Producer a m (Producer a m x)) Source #

splitAt is an improper lens that splits a Producer into two Producers after a fixed number of elements

groupBy :: Monad m => (a -> a -> Bool) -> Lens' (Producer a m x) (Producer a m (Producer a m x)) Source #

groupBy splits a Producer into two Producers after the first group of elements that are equal according to the equality predicate

group :: (Monad m, Eq a) => Lens' (Producer a m x) (Producer a m (Producer a m x)) Source #

Like groupBy, where the equality predicate is (==)

# Utilities

toParser :: Monad m => Consumer (Maybe a) m r -> Parser a m r Source #

Convert a Consumer to a Parser

Nothing signifies end of input

toParser_ :: Monad m => Consumer a m X -> Parser a m () Source #

Convert a never-ending Consumer to a Parser

parsed :: Monad m => Parser a m (Either e b) -> Producer a m r -> Producer b m (e, Producer a m r) Source #

Run a Parser repeatedly on a Producer, yielding each Right result

Returns the remainder of the Producer when the Parser returns Left

parsed_ :: Monad m => Parser a m (Maybe b) -> Producer a m r -> Producer b m (Producer a m r) Source #

Run a Parser repeatedly on a Producer, yielding each Just result

Returns the remainder of the Producer when the Parser returns Nothing

parseForever :: Monad m => (forall n. Monad n => Parser a n (Either r b)) -> Pipe a b m r Source #

Deprecated: Use parsed instead

Convert a Parser to a Pipe by running it repeatedly on the input

parseForever_ :: Monad m => (forall n. Monad n => Parser a n (Maybe b)) -> Pipe a b m () Source #

Deprecated: Use parsed_ instead

Variant of parseForever for parsers which return a Maybe instead of an Either

# Re-exports

Control.Monad.Trans.Class re-exports lift.

Control.Monad.Trans.State.Strict re-exports StateT, runStateT, evalStateT, and execStateT.

Pipes re-exports Producer, yield, and next`.

module Pipes