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authormichaelt <what_is_it_to_do_anything@yahoo.com>2016-02-06 23:58:47 -0500
committermichaelt <what_is_it_to_do_anything@yahoo.com>2016-02-06 23:58:47 -0500
commitda2f79d81f0544797e93d15bafde69d82be35f8a (patch)
tree0237afbabdb2dda8b09f4941575318c531726caf /Pipes
parentc3e06dbcca93dc0116a3f522fd514e95ec87d206 (diff)
downloadtext-pipes-da2f79d81f0544797e93d15bafde69d82be35f8a.tar.gz
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more documentation repairs
Diffstat (limited to 'Pipes')
-rw-r--r--Pipes/Prelude/Text.hs31
1 files changed, 18 insertions, 13 deletions
diff --git a/Pipes/Prelude/Text.hs b/Pipes/Prelude/Text.hs
index d573e51..ee3e104 100644
--- a/Pipes/Prelude/Text.hs
+++ b/Pipes/Prelude/Text.hs
@@ -42,7 +42,7 @@ import Prelude hiding (readFile, writeFile)
42 42
43>>> import Pipes 43>>> import Pipes
44>>> import qualified Pipes.Prelude as P 44>>> import qualified Pipes.Prelude as P
45>>> import qualified Pipes.Text.IO as Text 45>>> import qualified Pipes.Prelude.Text as Text
46>>> import qualified Data.Text as T 46>>> import qualified Data.Text as T
47>>> Text.runSafeT $ runEffect $ Text.stdinLn >-> P.take 3 >-> P.map T.toUpper >-> Text.writeFileLn "threelines.txt" 47>>> Text.runSafeT $ runEffect $ Text.stdinLn >-> P.take 3 >-> P.map T.toUpper >-> Text.writeFileLn "threelines.txt"
48one<Enter> 48one<Enter>
@@ -53,33 +53,38 @@ ONE
53TWO 53TWO
54THREE 54THREE
55 55
56 The point of view is very much that of @Pipes.Prelude@. It would still be the same even if 56 Here @runSafeT@ from @Pipes.Safe@ just makes sure to close any handles opened in its scope.
57 Otherwise the point of view is very much that of @Pipes.Prelude@, substituting @Text@ for @String@.
58 It would still be the same even if
57 we did something a bit more sophisticated, like run an ordinary attoparsec 'Text' parser on 59 we did something a bit more sophisticated, like run an ordinary attoparsec 'Text' parser on
58 each line, as is frequently desirable. Here we run 60 each line, as is frequently desirable. Here we use
59 a minimal attoparsec number parser, @scientific@, on separate lines of standard input, 61 a minimal attoparsec number parser, @scientific@, on separate lines of standard input,
60 dropping bad parses with @P.concat@: 62 dropping bad parses with @P.concat@:
61 63
62>>> import qualified Data.Attoparsec.Text as A 64>>> import Data.Attoparsec.Text (parseOnly, scientific)
63>>> P.toListM $ Text.stdinLn >-> P.map (A.parseOnly A.scientific) >-> P.concat >-> P.take 3 65>>> P.toListM $ Text.stdinLn >-> P.takeWhile (/= "quit") >-> P.map (parseOnly scientific) >-> P.concat
641<Enter> 661<Enter>
652<Enter> 672<Enter>
66bad<Enter> 68bad<Enter>
673<Enter> 693<Enter>
70quit<Enter>
68[1.0,2.0,3.0] 71[1.0,2.0,3.0]
69 72
70
71 The line-based operations are, however, subject to a number of caveats. 73 The line-based operations are, however, subject to a number of caveats.
72 First, where they read from a handle, they will of course happily 74 First, where they read from a handle, they will of course happily
73 accumulate indefinitely long lines. This is likely to be legitimate for input 75 accumulate indefinitely long lines. This is likely to be legitimate for input
74 typed in by a user, and for locally produced log files and other known material, but 76 typed in by a user, and for locally produced files of known characteristics, but
75 otherwise not. See the post on 77 otherwise not. See the post on
76 <http://www.haskellforall.com/2013/09/perfect-streaming-using-pipes-bytestring.html perfect streaming> 78 <http://www.haskellforall.com/2013/09/perfect-streaming-using-pipes-bytestring.html perfect streaming>
77 to see why @pipes-bytestring@ and this package take a different approach. Furthermore, 79 to see why @pipes-bytestring@ and this package, outside this module, take a different approach.
78 like those in @Data.Text.IO@, the operations use the system encoding (and @T.hGetLine@) 80 Furthermore, the line-based operations,
79 and thus are slower than the \'official\' route, which would use bytestring IO and 81 like those in @Data.Text.IO@, use the system encoding (and @T.hGetLine@)
80 the encoding and decoding functions in @Pipes.Text.Encoding@. Finally, they will generate 82 and thus are slower than the \'official\' route, which would use the very fast
81 text exceptions after the fashion of @Data.Text.Encoding@ rather than returning the 83 bytestring IO operations from @Pipes.ByteString@ and
82 undigested bytes in the style of @Pipes.Text.Encoding@ 84 encoding and decoding functions in @Pipes.Text.Encoding@. Finally, the line-based
85 operations will generate text exceptions after the fashion of
86 @Data.Text.Encoding@, rather than returning the undigested bytes in the
87 style of @Pipes.Text.Encoding@.
83 88
84-} 89-}
85 90