Copyright | (c) Bryan O'Sullivan 2009 2012 |
---|---|
License | BSD-style |
Maintainer | bos@serpentine.com |
Stability | experimental |
Portability | GHC |
Safe Haskell | None |
Language | Haskell2010 |
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!
This module provides a common stream fusion interface for text. The stream interface allows us to write text pipelines which do not allocate intermediate text values. For example, we could guarantee no intermediate text is allocated by writing the following:
getNucleotides ::Text
->Text
getNucleotides =unstream
.filter
isNucleotide .toLower
.stream
where isNucleotide chr = chr == 'a' || chr == 'c' || chr == 't' || chr == 'g'
Synopsis
- singleton :: Char -> Stream Char
- streamList :: [a] -> Stream a
- unstreamList :: Stream a -> [a]
- streamCString# :: Addr# -> Stream Char
- cons :: Char -> Stream Char -> Stream Char
- snoc :: Stream Char -> Char -> Stream Char
- append :: Stream Char -> Stream Char -> Stream Char
- head :: HasCallStack => Stream Char -> Char
- uncons :: Stream Char -> Maybe (Char, Stream Char)
- last :: HasCallStack => Stream Char -> Char
- tail :: HasCallStack => Stream Char -> Stream Char
- init :: HasCallStack => Stream Char -> Stream Char
- null :: Stream Char -> Bool
- lengthI :: Integral a => Stream Char -> a
- compareLengthI :: Integral a => Stream Char -> a -> Ordering
- isSingleton :: Stream Char -> Bool
- map :: (Char -> Char) -> Stream Char -> Stream Char
- intercalate :: Stream Char -> [Stream Char] -> Stream Char
- intersperse :: Char -> Stream Char -> Stream Char
- toCaseFold :: Stream Char -> Stream Char
- toLower :: Stream Char -> Stream Char
- toTitle :: Stream Char -> Stream Char
- toUpper :: Stream Char -> Stream Char
- justifyLeftI :: Integral a => a -> Char -> Stream Char -> Stream Char
- foldl :: (b -> Char -> b) -> b -> Stream Char -> b
- foldl' :: (b -> Char -> b) -> b -> Stream Char -> b
- foldl1 :: HasCallStack => (Char -> Char -> Char) -> Stream Char -> Char
- foldl1' :: HasCallStack => (Char -> Char -> Char) -> Stream Char -> Char
- foldr :: (Char -> b -> b) -> b -> Stream Char -> b
- foldr1 :: HasCallStack => (Char -> Char -> Char) -> Stream Char -> Char
- concat :: [Stream Char] -> Stream Char
- concatMap :: (Char -> Stream Char) -> Stream Char -> Stream Char
- any :: (Char -> Bool) -> Stream Char -> Bool
- all :: (Char -> Bool) -> Stream Char -> Bool
- maximum :: HasCallStack => Stream Char -> Char
- minimum :: HasCallStack => Stream Char -> Char
- scanl :: (Char -> Char -> Char) -> Char -> Stream Char -> Stream Char
- replicateCharI :: Integral a => a -> Char -> Stream Char
- replicateI :: Int64 -> Stream Char -> Stream Char
- unfoldr :: (a -> Maybe (Char, a)) -> a -> Stream Char
- unfoldrNI :: Integral a => a -> (b -> Maybe (Char, b)) -> b -> Stream Char
- take :: Integral a => a -> Stream Char -> Stream Char
- drop :: Integral a => a -> Stream Char -> Stream Char
- takeWhile :: (Char -> Bool) -> Stream Char -> Stream Char
- dropWhile :: (Char -> Bool) -> Stream Char -> Stream Char
- isPrefixOf :: Eq a => Stream a -> Stream a -> Bool
- elem :: Char -> Stream Char -> Bool
- filter :: (Char -> Bool) -> Stream Char -> Stream Char
- findBy :: (Char -> Bool) -> Stream Char -> Maybe Char
- indexI :: (HasCallStack, Integral a) => Stream Char -> a -> Char
- findIndexI :: Integral a => (Char -> Bool) -> Stream Char -> Maybe a
- countCharI :: Integral a => Char -> Stream Char -> a
- zipWith :: (a -> a -> b) -> Stream a -> Stream a -> Stream b
Creation and elimination
streamList :: [a] -> Stream a Source #
unstreamList :: Stream a -> [a] Source #
streamCString# :: Addr# -> Stream Char Source #
Stream the UTF-8-like packed encoding used by GHC to represent constant strings in generated code.
This encoding uses the byte sequence "xc0x80" to represent NUL, and the string is NUL-terminated.
Properties
unstream
.streamCString#
addr' addr#
Basic interface
lengthI :: Integral a => Stream Char -> a Source #
O(n) Returns the number of characters in a string.
compareLengthI :: Integral a => Stream Char -> a -> Ordering Source #
O(n) Compares the count of characters in a string to a number.
This function gives the same answer as comparing against the result
of lengthI
, but can short circuit if the count of characters is
greater than the number or if the stream can't possibly be as long
as the number supplied, and hence be more efficient.
isSingleton :: Stream Char -> Bool Source #
O(n) Indicate whether a string contains exactly one element.
Properties
isSingleton
.stream
=isSingleton
Transformations
intercalate :: Stream Char -> [Stream Char] -> Stream Char Source #
intercalate str strs interts the stream str in between the streams strs and concatenates the result.
Properties
intercalate
s =concat
.intersperse
s
intersperse :: Char -> Stream Char -> Stream Char Source #
O(n) Take a character and place it between each of the characters of a 'Stream Char'.
Properties
unstream
.intersperse
c .stream
=intersperse
c
Case conversion
With Unicode text, it is incorrect to use combinators like map
toUpper
to case convert each character of a string individually.
Instead, use the whole-string case conversion functions from this
module. For correctness in different writing systems, these
functions may map one input character to two or three output
characters.
toCaseFold :: Stream Char -> Stream Char Source #
O(n) Convert a string to folded case. This function is mainly useful for performing caseless (or case insensitive) string comparisons.
A string x
is a caseless match for a string y
if and only if:
toCaseFold
x ==toCaseFold
y
The result string may be longer than the input string, and may
differ from applying toLower
to the input string. For instance,
the Armenian small ligature men now (U+FB13) is case folded to the
bigram men now (U+0574 U+0576), while the micro sign (U+00B5) is
case folded to the Greek small letter letter mu (U+03BC) instead of
itself.
toLower :: Stream Char -> Stream Char Source #
O(n) Convert a string to lower case, using simple case conversion. The result string may be longer than the input string. For instance, the Latin capital letter I with dot above (U+0130) maps to the sequence Latin small letter i (U+0069) followed by combining dot above (U+0307).
Properties
unstream
.toLower
.stream
=toLower
toTitle :: Stream Char -> Stream Char Source #
O(n) Convert a string to title case, using simple case conversion.
The first letter of the input is converted to title case, as is every subsequent letter that immediately follows a non-letter. Every letter that immediately follows another letter is converted to lower case.
The result string may be longer than the input string. For example, the Latin small ligature fl (U+FB02) is converted to the sequence Latin capital letter F (U+0046) followed by Latin small letter l (U+006C).
Note: this function does not take language or culture specific rules into account. For instance, in English, different style guides disagree on whether the book name "The Hill of the Red Fox" is correctly title cased—but this function will capitalize every word.
Properties
unstream
.toTitle
.stream
=toTitle
Justification
Folds
Special folds
Construction
Scans
Generation and unfolding
replicateCharI :: Integral a => a -> Char -> Stream Char Source #
O(n) replicateCharI
n
c
is a Stream
Char
of length n
with c
the
value of every element.
replicateI :: Int64 -> Stream Char -> Stream Char Source #
O(n*m) replicateI
n
t
is a Stream
Char
consisting of the input
t
repeated n
times.
unfoldr :: (a -> Maybe (Char, a)) -> a -> Stream Char Source #
O(n), where n
is the length of the result. The unfoldr function
is analogous to the List unfoldr
. unfoldr builds a stream
from a seed value. The function takes the element and returns
Nothing if it is done producing the stream or returns Just
(a,b), in which case, a is the next Char in the string, and b is
the seed value for further production.
Properties
unstream
.unfoldr
f z =unfoldr
f z
Substrings
Breaking strings
Predicates
isPrefixOf :: Eq a => Stream a -> Stream a -> Bool Source #
O(n) The isPrefixOf
function takes two Stream
s and returns
True
iff the first is a prefix of the second.
Properties
isPrefixOf
(stream
t1) (stream
t2) =isPrefixOf
t1 t2
Searching
Indexing
findIndexI :: Integral a => (Char -> Bool) -> Stream Char -> Maybe a Source #
The findIndexI
function takes a predicate and a stream and
returns the index of the first element in the stream satisfying the
predicate.
Properties
findIndexI
p .stream
=findIndex
p
countCharI :: Integral a => Char -> Stream Char -> a Source #
O(n) The countCharI
function returns the number of times the
query element appears in the given stream.
Properties
countCharI
c .stream
=countChar
c