The enumerator package

[Tags: library, mit]

Typical buffer–based incremental I/O is based around a single loop, which reads data from some source (such as a socket or file), transforms it, and generates one or more outputs (such as a line count, HTTP responses, or modified file). Although efficient and safe, these loops are all single–purpose; it is difficult or impossible to compose buffer–based processing loops.

Haskell’s concept of “lazy I/O” allows pure code to operate on data from an external source. However, lazy I/O has several shortcomings. Most notably, resources such as memory and file handles can be retained for arbitrarily long periods of time, causing unpredictable performance and error conditions.

Enumerators are an efficient, predictable, and safe alternative to lazy I/O. Discovered by Oleg Kiselyov, they allow large datasets to be processed in near–constant space by pure code. Although somewhat more complex to write, using enumerators instead of lazy I/O produces more correct programs.

This library contains an enumerator implementation for Haskell, designed to be both simple and efficient. Three core types are defined, along with numerous helper functions:


Versions0.1, 0.1.1, 0.2, 0.2.1, 0.3,, 0.4,,, 0.4.1, 0.4.2, 0.4.3,, 0.4.4, 0.4.5, 0.4.6, 0.4.7, 0.4.8, 0.4.9,, 0.4.10, 0.4.11, 0.4.12, 0.4.13,, 0.4.14, 0.4.15, 0.4.16, 0.4.17, 0.4.18, 0.4.19, 0.4.20
Dependenciesbase (==3.*), bytestring (==0.9.*), extensible-exceptions (==0.1.*), text (>=0.7 && <0.12), transformers (==0.2.*) or
base (==4.*), bytestring (==0.9.*), text (>=0.7 && <0.12), transformers (==0.2.*)
CopyrightCopyright (c) John Millikin 2010
AuthorJohn Millikin <>
CategoryData, Enumerator
Home page
Source repositoryhead: bzr branch
Upload dateSat Mar 26 04:43:40 UTC 2011
Uploaded byJohnMillikin
DistributionsDebian:0.4.19, Fedora:0.4.19, FreeBSD:0.4.19, NixOS:0.4.20
Downloads19403 total (1752 in last 30 days)




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