|Copyright||(c) Bryan O'Sullivan 2009 2012|
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!
Common stream fusion functionality for text.
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.
O(n) Adds a character to the front of a Stream Char.
O(n) Adds a character to the end of a stream.
O(n) Appends one Stream to the other.
O(1) Returns the first character of a Text, which must be non-empty. Subject to array fusion.
O(1) Returns the first character and remainder of a 'Stream Char', or
Nothing if empty. Subject to array fusion.
O(n) Returns the last character of a 'Stream Char', which must be non-empty.
O(1) Returns all characters after the head of a Stream Char, which must be non-empty.
O(1) Returns all but the last character of a Stream Char, which must be non-empty.
O(1) Tests whether a Stream Char is empty or not.
O(n) Returns the number of characters in a string.
O(n) Compares the count of characters in a string to a number. Subject to fusion.
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.
O(n) Indicate whether a string contains exactly one element.
f xs is the Stream Char obtained by applying
f to each element of
O(n) Take a character and place it between each of the characters of a 'Stream Char'.
With Unicode text, it is incorrect to use combinators like
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.
O(n) Convert a string to folded case. This function is mainly useful for performing caseless (or case insensitive) string comparisons.
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.
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).
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.
O(n) Convert a string to upper case, using simple case conversion. The result string may be longer than the input string. For instance, the German eszett (U+00DF) maps to the two-letter sequence SS.
foldl, applied to a binary operator, a starting value (typically the left-identity of the operator), and a Stream, reduces the Stream using the binary operator, from left to right.
A strict version of foldl.
foldl1 is a variant of foldl that has no starting value argument, and thus must be applied to non-empty Streams.
A strict version of foldl1.
foldr, applied to a binary operator, a starting value (typically the right-identity of the operator), and a stream, reduces the stream using the binary operator, from right to left.
foldr1 is a variant of
foldr that has no starting value argument, and thus must be applied to non-empty streams. Subject to array fusion.
O(n) Concatenate a list of streams. Subject to array fusion.
Map a function over a stream that results in a stream and concatenate the results.
p xs determines if any character in the stream
xs satisfies the predicate
p xs determines if all characters in the
xs satisfy the predicate
O(n) maximum returns the maximum value from a stream, which must be non-empty.
O(n) minimum returns the minimum value from a
Text, which must be non-empty.
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.
unfoldrNI builds a stream from a seed value. However, the length of the result is limited by the first argument to
unfoldrNI. This function is more efficient than
unfoldr when the length of the result is known.
take n, applied to a stream, returns the prefix of the stream of length
n, or the stream itself if
n is greater than the length of the stream.
drop n, applied to a stream, returns the suffix of the stream after the first
n characters, or the empty stream if
n is greater than the length of the stream.
takeWhile, applied to a predicate
p and a stream, returns the longest prefix (possibly empty) of elements that satisfy
elem is the stream membership predicate.
filter, applied to a predicate and a stream, returns a stream containing those characters that satisfy the predicate.
O(n) Stream index (subscript) operator, starting from 0.
findIndexI function takes a predicate and a stream and returns the index of the first element in the stream satisfying the predicate.
countCharI function returns the number of times the query element appears in the given stream.
zip by zipping with the function given as the first argument, instead of a tupling function.
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Licensed under a BSD-style license (see top of the page).