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| author |   Robin H. Johnson <robbat2@gentoo.org> | 2015-08-08 13:49:04 -0700 |
|---|---|---|
| committer | Robin H. Johnson <robbat2@gentoo.org> | 2015-08-08 17:38:18 -0700 |
| commit | 56bd759df1d0c750a065b8c845e93d5dfa6b549d (patch) | |
| tree | 3f91093cdb475e565ae857f1c5a7fd339e2d781e /dev-haskell/chasingbottoms/metadata.xml | |
| download | gentoo-56bd759df1d0c750a065b8c845e93d5dfa6b549d.tar.gz gentoo-56bd759df1d0c750a065b8c845e93d5dfa6b549d.tar.bz2 gentoo-56bd759df1d0c750a065b8c845e93d5dfa6b549d.zip | |
proj/gentoo: Initial commit
This commit represents a new era for Gentoo:
Storing the gentoo-x86 tree in Git, as converted from CVS.
This commit is the start of the NEW history.
Any historical data is intended to be grafted onto this point.
Creation process:
1. Take final CVS checkout snapshot
2. Remove ALL ChangeLog* files
3. Transform all Manifests to thin
4. Remove empty Manifests
5. Convert all stale $Header$/$Id$ CVS keywords to non-expanded Git $Id$
5.1. Do not touch files with -kb/-ko keyword flags.
Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>
X-Thanks: Alec Warner <antarus@gentoo.org> - did the GSoC 2006 migration tests
X-Thanks: Robin H. Johnson <robbat2@gentoo.org> - infra guy, herding this project
X-Thanks: Nguyen Thai Ngoc Duy <pclouds@gentoo.org> - Former Gentoo developer, wrote Git features for the migration
X-Thanks: Brian Harring <ferringb@gentoo.org> - wrote much python to improve cvs2svn
X-Thanks: Rich Freeman <rich0@gentoo.org> - validation scripts
X-Thanks: Patrick Lauer <patrick@gentoo.org> - Gentoo dev, running new 2014 work in migration
X-Thanks: Michał Górny <mgorny@gentoo.org> - scripts, QA, nagging
X-Thanks: All of other Gentoo developers - many ideas and lots of paint on the bikeshed
Diffstat (limited to 'dev-haskell/chasingbottoms/metadata.xml')
| -rw-r--r-- | dev-haskell/chasingbottoms/metadata.xml | 99 |
1 files changed, 99 insertions, 0 deletions
diff --git a/dev-haskell/chasingbottoms/metadata.xml b/dev-haskell/chasingbottoms/metadata.xml new file mode 100644 index 000000000000..bf0a95f2eed0 --- /dev/null +++ b/dev-haskell/chasingbottoms/metadata.xml @@ -0,0 +1,99 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd"> +<pkgmetadata> + <herd>haskell</herd> + <longdescription> + Do you ever feel the need to test code involving bottoms (e.g. calls to + the @error@ function), or code involving infinite values? Then this + library could be useful for you. + + It is usually easy to get a grip on bottoms by showing a value and + waiting to see how much gets printed before the first exception is + encountered. However, that quickly gets tiresome and is hard to automate + using e.g. QuickCheck + (<http://www.cse.chalmers.se/~rjmh/QuickCheck/>). With this library you + can do the tests as simply as the following examples show. + + Testing explicitly for bottoms: + + [@> isBottom (head [\])@] @True@ + + [@> isBottom bottom@] @True@ + + [@> isBottom (\\_ -> bottom)@] @False@ + + [@> isBottom (bottom, bottom)@] @False@ + + Comparing finite, partial values: + + [@> ((bottom, 3) :: (Bool, Int)) ==! (bottom, 2+5-4)@] @True@ + + [@> ((bottom, bottom) :: (Bool, Int)) <! (bottom, 8)@] @True@ + + Showing partial and infinite values (@\\\/!@ is join and @\/\\!@ is meet): + + [@> approxShow 4 $ (True, bottom) \\\/! (bottom, \'b\')@] @\"Just (True, \'b\')\"@ + + [@> approxShow 4 $ (True, bottom) \/\\! (bottom, \'b\')@] @\"(_|_, _|_)\"@ + + [@> approxShow 4 $ ([1..\] :: [Int\])@] @\"[1, 2, 3, _\"@ + + [@> approxShow 4 $ (cycle [bottom\] :: [Bool\])@] @\"[_|_, _|_, _|_, _\"@ + + Approximately comparing infinite, partial values: + + [@> approx 100 [2,4..\] ==! approx 100 (filter even [1..\] :: [Int\])@] @True@ + + [@> approx 100 [2,4..\] \/=! approx 100 (filter even [bottom..\] :: [Int\])@] @True@ + + The code above relies on the fact that @bottom@, just as @error + \"...\"@, @undefined@ and pattern match failures, yield + exceptions. Sometimes we are dealing with properly non-terminating + computations, such as the following example, and then it can be nice to + be able to apply a time-out: + + [@> timeOut' 1 (reverse [1..5\])@] @Value [5,4,3,2,1]@ + + [@> timeOut' 1 (reverse [1..\])@] @NonTermination@ + + The time-out functionality can be used to treat \"slow\" computations as + bottoms: + + [@> let tweak = Tweak &#x7b; approxDepth = Just 5, timeOutLimit = Just 2 &#x7d;@] + + [@> semanticEq tweak (reverse [1..\], [1..\]) (bottom :: [Int\], [1..\] :: [Int\])@] @True@ + + [@> let tweak = noTweak &#x7b; timeOutLimit = Just 2 &#x7d;@] + + [@> semanticJoin tweak (reverse [1..\], True) ([\] :: [Int\], bottom)@] @Just ([],True)@ + + This can of course be dangerous: + + [@> let tweak = noTweak &#x7b; timeOutLimit = Just 0 &#x7d;@] + + [@> semanticEq tweak (reverse [1..100000000\]) (bottom :: [Integer\])@] @True@ + + Timeouts can also be applied to @IO@ computations: + + [@> let primes = unfoldr (\\(x:xs) -> Just (x, filter ((\/= 0) . (\`mod\` x)) xs)) [2..\]@] + + [@> timeOutMicro 100 (print $ filter ((== 1) . (\`mod\` 83)) primes)@] @[167,499,9NonTermination@ + + [@> timeOutMicro 100 (print $ take 6 $ filter ((== 1) . (\`mod\` 83)) primes)@] @[167,499,997,1163,1993NonTermination@ + + [@> timeOutMicro 100 (print $ take 6 $ filter ((== 1) . (\`mod\` 83)) primes)@] @[167,499,997,1163,1993,2657]@ + + [@ @] @Value ()@ + + For the underlying theory and a larger example involving use of + QuickCheck, see the article \"Chasing Bottoms, A Case Study in Program + Verification in the Presence of Partial and Infinite Values\" + (<http://www.cse.chalmers.se/~nad/publications/danielsson-jansson-mpc2004.html>). + + The code has been tested using GHC. Most parts can probably be + ported to other Haskell compilers, but this would require some work. + The @TimeOut@ functions require preemptive scheduling, and most of + the rest requires @Data.Generics@; @isBottom@ only requires + exceptions, though. + </longdescription> +</pkgmetadata> |