Data.Text.Internal.Fusion

text-1.2.1.3: An efficient packed Unicode text type.

Copyright | (c) Tom Harper 2008-2009, (c) Bryan O'Sullivan 2009-2010, (c) Duncan Coutts 2009
License | BSD-style
Maintainer | bos@serpentine.com
Stability | experimental
Portability | GHC
Safe Haskell | None
Language | Haskell98

Data.Text.Internal.Fusion

Contents

- Types
- Creation and elimination
- Transformations
- Construction
  - Scans
  - Accumulating maps
  - Generation and unfolding
- Indexing

Description

Warning: this is an internal module, and does not have a stable API or name. Functions in this module may not check or enforce preconditions expected by public modules. Use at your own risk!

Text manipulation functions represented as fusible operations over streams.

Synopsis

- data Stream a = forall s . Stream (s -> Step s a) !s !Size
- data Step s a
  - = Done
  - | Skip !s
  - | Yield !a !s
- stream :: Text -> Stream Char
- unstream :: Stream Char -> Text
- reverseStream :: Text -> Stream Char
- length :: Stream Char -> Int
- reverse :: Stream Char -> Text
- reverseScanr :: (Char -> Char -> Char) -> Char -> Stream Char -> Stream Char
- mapAccumL :: (a -> Char -> (a, Char)) -> a -> Stream Char -> (a, Text)
- unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> Stream Char
- index :: Stream Char -> Int -> Char
- findIndex :: (Char -> Bool) -> Stream Char -> Maybe Int
- countChar :: Char -> Stream Char -> Int

# Types

data Stream a

Constructors

forall s . Stream (s -> Step s a) !s !Size |

Instances

Eq a => Eq (Stream a) |
Ord a => Ord (Stream a) |

data Step s a

Intermediate result in a processing pipeline.

Constructors

Done |
Skip !s |
Yield !a !s |

# Creation and elimination

stream :: Text -> Stream Char

O(n) Convert a `Text` into a 'Stream Char'.

unstream :: Stream Char -> Text

O(n) Convert a 'Stream Char' into a `Text`.

reverseStream :: Text -> Stream Char

O(n) Convert a `Text` into a 'Stream Char', but iterate backwards.

length :: Stream Char -> Int

# Transformations

reverse :: Stream Char -> Text

O(n) Reverse the characters of a string.

# Construction

## Scans

reverseScanr :: (Char -> Char -> Char) -> Char -> Stream Char -> Stream Char

O(n) Perform the equivalent of `scanr` over a list, only with the input and result reversed.

## Accumulating maps

mapAccumL :: (a -> Char -> (a, Char)) -> a -> Stream Char -> (a, Text)

O(n) Like a combination of `map` and `foldl'`. Applies a function to each element of a `Text`, passing an accumulating parameter from left to right, and returns a final `Text`.

## Generation and unfolding

unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> Stream Char

O(n) Like `unfoldr`, `unfoldrN` builds a stream from a seed value. However, the length of the result is limited by the first argument to `unfoldrN`. This function is more efficient than `unfoldr` when the length of the result is known.

# Indexing

index :: Stream Char -> Int -> Char

O(n) stream index (subscript) operator, starting from 0.

findIndex :: (Char -> Bool) -> Stream Char -> Maybe Int

The `findIndex` function takes a predicate and a stream and returns the index of the first element in the stream satisfying the predicate.

countChar :: Char -> Stream Char -> Int

O(n) The `count` function returns the number of times the query element appears in the given stream.