co-log-core

Composable Contravariant Comonadic Logging Library

Version on this page:	0.2.0.0
LTS Haskell 24.17:	0.3.2.5
Stackage Nightly 2025-10-31:	0.3.2.5
Latest on Hackage:	0.3.2.5

See all snapshots co-log-core appears in

MPL-2.0 licensed by Dmitrii Kovanikov

Maintained by Kowainik

This version can be pinned in stack with:co-log-core-0.2.0.0@sha256:ca2368435e7516df08f928c6be99e44f1574139d97ece023fab0d8de72d95b12,3084

Module documentation for 0.2.0.0

Colog
- Colog.Core

Depends on 1 package(full list with versions):

base

Used by 1 package in lts-14.20(full list with versions):

co-log


`co-log-core`
`co-log`
`co-log-polysemy`

co-log is a composable and configurable logging framework. The idea of the approach is described in the following blog post:

co-log: Composable Contravariant Combinatorial Comonadic Configurable Convenient Logging

The repository contains the following packages:

co-log-core: lightweight package with basic data types and general idea.
co-log: taggless final implementation of logging library based on co-log-core.
co-log-polysemy: implementation of logging library based on co-log-core and the polysemy extensible effects library.
co-log-benchmark: Benchmarks of the co-log library.

See the following tutorial series about the library:

Benchmarks

co-log is compared with basic functions like putStrLn. Since IO overhead is big enough, every benchmark dumps 10K messages to output. If benchmark name doesn’t contain Message then this benchmark simply dumps string "message" to output, otherwise it works with Message data type from the co-log library.

Benchmarks	Time for 10K messages
`Prelude.putStrLn`	`5.117ms`
`Text.putStrLn`	`9.220ms`
`ByteString.putStrLn`	`2.971ms`
`mempty`	`1.181ms`
`logStringStdout`	`5.107ms`
`logPrint`	`5.248ms`
`logTextStdout`	`5.351ms`
`logByteStringStdout`	`2.933ms`
`logByteStringStderr`	`17.482ms`
`ByteString > (stdout <> stderr)`	`17.715ms`
`Message > format > stdout`	`9.188ms`
`Message > format > ByteString > stdout`	`3.524ms`
`Message{callstack} > format > stdout`	`9.139ms`
`Message{callstack:5} > format > stdout`	`9.464ms`
`Message{callstack:50} > format > stdout`	`9.439ms`
`Message{Time,ThreadId} > format > stdout`	`54.160ms`
`Message{Time,ThreadId} > format > ByteString > stdout`	`54.137ms`

Changes

Change log

co-log-core uses PVP Versioning. The change log is available on GitHub.

0.1.2.0 — May 5, 2019

#85: Move overLogAction to HasLog typeclass
#101: Add logActionL lens with default implementation to HasLog type class.
#99: Add comonadic combinators: duplicate and multiplicate.
#78: Improve documentation significantly.

0.1.1 — Nov 15, 2018

#63: Add logPrint, logPrintStderr, logPrintHandle and withLogPrintFile to Colog.Core.IO.
#46: Moves logStringStdout, logStringStderr, logStringHandle, withLogStringFile from Colog.Actions to Colog.Core.IO.
#48: Adds liftLogIO function.
#49: Add <& and &>operators for unLogAction.
#47: Add doctest tests.
#13: Add .cabal file description and improve documentation.
#39: Support GHC-8.2.2 and GHC-8.6.2.

0.1.0

#38: Rename cbind to cmapM.
#37: Add base bounds.

0.0.0

Initially created.