A stream is a (continuing) sequence of elements bundled in Chunks. The first two variants indicate termination of the stream. Chunk a gives the currently available part of the stream. The stream is not terminated yet. The case (null Chunk) signifies a stream with no currently available data but which is still continuing. A stream processor should, informally speaking, ``suspend itself'' and wait for more data to arrive.

Iteratee -- a generic stream processor, what is being folded over a stream When Iteratee is in the done state, it contains the computed result and the remaining part of the stream. In the cont state, the iteratee has not finished the computation and needs more input. We assume that all iteratees are good -- given bounded input, they do the bounded amount of computation and take the bounded amount of resources. The monad m describes the sort of computations done by the iteratee as it processes the stream. The monad m could be the identity monad (for pure computations) or the IO monad (to let the iteratee store the stream processing results as they are computed). We also assume that given a terminated stream, an iteratee moves to the done state, so the results computed so far could be returned.

The type of the converter from the stream with elements el_outer to the stream with element el_inner. The result is the iteratee for the outer stream that uses an `IterateeG el_inner m a' to process the embedded, inner stream as it reads the outer stream.

Each enumerator takes an iteratee and returns an iteratee an Enumerator is an iteratee transformer. The enumerator normally stops when the stream is terminated or when the iteratee moves to the done state, whichever comes first. When to stop is of course up to the enumerator...

More general enumerator type: enumerator that maps streams (not necessarily in lock-step). This is a flattened (`joinI-ed') EnumeratorN sfrom elfrom sto elto m a

The following is a variant of join in the IterateeGM s el m monad When el' is the same as el, the type of joinI is indeed that of true monadic join. However, joinI is subtly different: since generally el' is different from el, it makes no sense to continue using the internal, IterateeG el' m a: we no longer have elements of the type el' to feed to that iteratee. We thus send EOF to the internal Iteratee and propagate its result. This join function is useful when dealing with `derived iteratees' for embedded/nested streams. In particular, joinI is useful to process the result of take, mapStream, or convStream below.

Lift an IterGV result into an IterateeG

Check if a stream has finished (EOF).

Run an IterateeG and get the result. An EOF is sent to the iteratee as it is run.

A variant of join for Iteratees in a monad.

Read a stream to the end and return all of its elements as a list

Read a stream to the end and return all of its elements as a stream

If the iteratee (IterGV) has finished, return its value. If it has not finished then apply it to the given EnumeratorGM. If in error, throw the error.

Layer a monad transformer over the inner monad.

Produce the EOF error message. If the stream was terminated because of an error, keep the original error message.

Report and propagate an error. Disregard the input first and then propagate the error.

Check if an iteratee produces an error. Returns 'Right a' if it completes without errors, otherwise 'Left ErrMsg' checkErr is useful for iteratees that may not terminate, such as head with an empty stream. In particular, it enables them to be used with convStream.

The analogue of List.break It takes an element predicate and returns the (possibly empty) prefix of the stream. None of the characters in the string satisfy the character predicate. If the stream is not terminated, the first character on the stream satisfies the predicate.

Skip all elements while the predicate is true. This is the analogue of List.dropWhile

Skip n elements of the stream, if there are that many This is the analogue of List.drop

The identity iterator. Doesn't do anything.

Attempt to read the next element of the stream and return it Raise a (recoverable) error if the stream is terminated

Given a sequence of characters, attempt to match them against the characters on the stream. Return the count of how many characters matched. The matched characters are removed from the stream. For example, if the stream contains abd, then (heads abc) will remove the characters ab and return 2.

Look ahead at the next element of the stream, without removing it from the stream. Return (Just c) if successful, return Nothing if the stream is terminated (by EOF or an error)

Skip the rest of the stream

Return the total length of the stream

Read n elements from a stream and apply the given iteratee to the stream of the read elements. Unless the stream is terminated early, we read exactly n elements (even if the iteratee has accepted fewer).

Read n elements from a stream and apply the given iteratee to the stream of the read elements. If the given iteratee accepted fewer elements, we stop. This is the variation of take with the early termination of processing of the outer stream once the processing of the inner stream finished early.

Map the stream: yet another iteratee transformer Given the stream of elements of the type el and the function el->el', build a nested stream of elements of the type el' and apply the given iteratee to it. Note the contravariance

Map a stream without changing the element type. For StreamChunks with limited element types (e.g. bytestrings) this can be much more efficient than regular mapStream

Yet another stream mapping function. For container instances with class contexts, such as uvector or storablevector, this allows the native map function to be used and is likely to be much more efficient than the standard mapStream.

Convert one stream into another, not necessarily in lockstep The transformer mapStream maps one element of the outer stream to one element of the nested stream. The transformer below is more general: it may take several elements of the outer stream to produce one element of the inner stream, or the other way around. The transformation from one stream to the other is specified as IterateeGM s el m (Maybe (s' el')). The Maybe type is in case of errors (or end of stream).

Creates an enumerator with only elements from the stream that satisfy the predicate function.

Left-associative fold.

Left-associative fold that is strict in the accumulator.

Variant of foldl with no base case. Requires at least one element in the stream.

Sum of a stream.

Product of a stream

The most primitive enumerator: applies the iteratee to the terminated stream. The result is the iteratee usually in the done state.

Another primitive enumerator: report an error

The pure 1-chunk enumerator It passes a given list of elements to the iteratee in one chunk This enumerator does no IO and is useful for testing of base parsing

The pure n-chunk enumerator It passes a given chunk of elements to the iteratee in n chunks This enumerator does no IO and is useful for testing of base parsing and handling of chunk boundaries

The composition of two enumerators: essentially the functional composition It is convenient to flip the order of the arguments of the composition though: in e1 >. e2, e1 is executed first

Enumerate two iteratees over a single stream simultaneously.

Seek to a position in the stream