Moduletrifecta-2.1.4Haskell2010

Text.Trifecta.Util.It

harder, better, faster, stronger...

1 type
8 values

Packagetrifecta-2.1.4
Exports9
LanguageHaskell2010
LicenceBSD-3-Clause
SourceIt.hs

datadata It r a

It is an Iteratee that can produce partial results.

It r a consumes a feed of rs and produces as on the way. New values can be fed using simplifyIt, the current (partial or final) result is extracted using extract.

Example2 expressions

>>> let keepIt    a = Pure a>>> let replaceIt a = It a replaceIt

Example1 expression

>>> extract (keepIt 0)0

Example1 expression

>>> extract (replaceIt 0)0

Example1 expression

>>> extract (simplifyIt (keepIt 0) 5)0

Example1 expression

>>> extract (simplifyIt (replaceIt 0) 5)5

Constructors

Pure a
Final result, rest of the feed is discarded
It a (r -> It r a)
Intermediate result, consumed values produce new results

Instances7Profunctor, Monad, Functor, Applicative, Comonad, ComonadApply, …

Profunctor ItDefined in trifecta-2.1.4 · Text.Trifecta.Util.It
Monad (It r)Defined in trifecta-2.1.4 · Text.Trifecta.Util.It
Functor (It r)Defined in trifecta-2.1.4 · Text.Trifecta.Util.It
Applicative (It r)Defined in trifecta-2.1.4 · Text.Trifecta.Util.It
Comonad (It r)Defined in trifecta-2.1.4 · Text.Trifecta.Util.It
It is a cofree comonad
ComonadApply (It r)Defined in trifecta-2.1.4 · Text.Trifecta.Util.It
Show a => Show (It r a)Defined in trifecta-2.1.4 · Text.Trifecta.Util.It

valueneedIt

:: a
Initial result
-> (r -> Maybe a)
Produce a result if possible
-> It r a

Consumes input until a value can be produced.

Example1 expression

>>> :{let needTen = needIt 0 (\n -> if n < 10 then Nothing else Just n) :: It Int Int:}

Example1 expression

>>> extract needTen0

Example1 expression

>>> extract (simplifyIt needTen 5)0

Example1 expression

>>> extract (simplifyIt needTen 11)11

Example1 expression

>>> extract (simplifyIt (simplifyIt (simplifyIt needTen 5) 11) 15)11

valuewantIt

:: a
Initial result
-> (r -> (# Bool, a #))
Produce a partial or final result
-> It r a

Consumes input and produces partial results until a condition is met. Unlike needIt, partial results are already returned when the condition is not fulfilled yet.

>>> :{
let wantTen :: It Int Int
    wantTen = wantIt 0 (\n -> (# n >= 10, n #))
:}

>>> extract wantTen
0

>>> extract (simplifyIt wantTen 5)
5

>>> extract (simplifyIt wantTen 11)
11

>>> extract (simplifyIt (simplifyIt (simplifyIt wantTen 5) 11) 15)
11

valuesimplifyIt :: It r a -> r -> It r a

Feed a value to It, obtaining a new (partial or final) result.

valuefoldIt :: (a -> o) -> (a -> (r -> o) -> o) -> It r a -> o

The generalized fold (Böhm-Berarducci decoding) over 'It r a'.

foldIt satisfies the property:

foldIt Pure It = id

valuerunIt :: (a -> o) -> (a -> (r -> It r a) -> o) -> It r a -> o

Scott decoding of 'It r a'.

The scott decoding is similar to the generalized fold over a data type, but leaves the recursion step to the calling function.

runIt satiesfies the property:

runIt Pure It = id

See also the Scott decoding of lists:

runList :: (a -> [a] -> b) -> b -> [a] -> b

and compare it with foldr (the Böhm-Berarducci decoding for lists):

foldr :: (a -> b -> b) -> b -> [a] -> b

valuefillIt :: r -> (Delta -> ByteString -> r) -> Delta -> It Rope r

Given a position, go there, and grab the rest of the line forward from that point.

Example2 expressions

>>> :set -XOverloadedStrings>>> let secondLine = fillIt Nothing (const Just) (delta ("foo\nb" :: Strict.ByteString))

Example1 expression

>>> extract secondLineNothing

Example1 expression

>>> extract (simplifyIt secondLine (ropeBS "foo"))Nothing

Example1 expression

>>> extract (simplifyIt secondLine (ropeBS "foo\nbar"))Just "ar"

Example1 expression

>>> extract (simplifyIt secondLine (ropeBS "foo\nbar\nbaz"))Just "ar\n"

valuerewindIt :: Delta -> It Rope (Maybe ByteString)

Return the text of the line that contains a given position

Example2 expressions

>>> :set -XOverloadedStrings>>> let secondLine = rewindIt (delta ("foo\nb" :: Strict.ByteString))

Example1 expression

>>> extract secondLineNothing

Example1 expression

>>> extract (simplifyIt secondLine (ropeBS "foo"))Nothing

Example1 expression

>>> extract (simplifyIt secondLine (ropeBS "foo\nbar"))Just "bar"

Example1 expression

>>> extract (simplifyIt secondLine (ropeBS "foo\nbar\nbaz"))Just "bar\n"

valuesliceIt :: Delta -> Delta -> It Rope ByteString

Return the text between two offsets.

Example2 expressions

>>> :set -XOverloadedStrings>>> let secondLine = sliceIt (delta ("foo\n" :: Strict.ByteString)) (delta ("foo\nbar\n" :: Strict.ByteString))

Example1 expression

>>> extract secondLine""

Example1 expression

>>> extract (simplifyIt secondLine (ropeBS "foo"))""

Example1 expression

>>> extract (simplifyIt secondLine (ropeBS "foo\nbar"))"bar"

Example1 expression

>>> extract (simplifyIt secondLine (ropeBS "foo\nbar\nbaz"))"bar\n"