https://github.com/chrispenner/lens-csv

Lensy interface for parsing CSV's
https://github.com/chrispenner/lens-csv

csv-parsing hacktoberfest lenses optics

Last synced: about 2 months ago
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Lensy interface for parsing CSV's

• Host: GitHub
• URL: https://github.com/chrispenner/lens-csv
• Owner: ChrisPenner
• License: bsd-3-clause
• Created: 2019-11-27T01:42:12.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2020-10-20T01:26:26.000Z (over 4 years ago)
• Last Synced: 2024-04-26T02:02:37.490Z (about 1 year ago)
• Topics: csv-parsing, hacktoberfest, lenses, optics
• Language: Haskell
• Homepage:
• Size: 122 KB
• Stars: 41
• Watchers: 8
• Forks: 2
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • Changelog: ChangeLog.md
  • License: LICENSE

Awesome Lists containing this project

README

        
# lens-csv

* Docs are on [Hackage](http://hackage.haskell.org/package/lens-csv)

If you enjoy working with lenses (or need a hand learning how they work) my book [Optics By Example](https://leanpub.com/optics-by-example/) is a great place to learn more!

[![Optics By Example](./optics-by-example.png)](https://leanpub.com/optics-by-example/)

A lensy layer on top of Cassava which affords streaming, traversable, CSV parsing.

Still experimental (but working). Please file an issue if there are features the library doesn't support.

Example:

```haskell

>>> import Data.ByteString.Lazy as BL

>>> myCsv <- BL.readFile "./data/simple.csv"

>>> myCsv ^.. namedCsv . taking 2 rows . column @String "state_code" 

[ "NY"

, "CA"

]

>>> myCsv ^.. namedCsv . taking 2 rows . _NamedRecord @(M.Map String String)

[ fromList [("population","19540000"), ("state_code","NY")]

, fromList [("population","39560000"), ("state_code","CA")]

]

-- For csv files without headers

>>> myCsv ^.. csv . taking 2 rows . _Record @[String]

[ ["state_code", "population"]

, ["NY"        , "19540000"]

]

-- 'column' infers whether it's a named or unnamed csv and accepts the appropriate index type (either ByteString or Int)

>>> myCsv ^.. csv . rows . column @Int 1

[19540000,39560000]

-- Use traversals to edit cells 'in-place' (add 1337 to California's population)

>>> BL.putStrLn $ myCsv & namedCsv . row 1 . column @Int "population" +~ 1337

state_code,population

NY,19540000

CA,39561337

```