Text.PrettyPrint.Tabulate.Example

Example usage of ppTable library

Setup extensions

:set -XDeriveGeneric
:set -XDeriveDataTypeable

Required imports

Generics and Data need to be imported since and type that will needs to be printed in tabular format needs to derive from Generic and Data

import qualified GHC.Generics as G
import Data.Data

Import Tabulate

Tabulate class and ppTable function are the only declarations to quickly using the library for printing in tabular format

import qualified Text.PrettyPrint.Tabulate as T

Use any Traversable

The data type that we will print in tabular format will have to be an element of a Traversable instance. The ppTable library provides default instances for Map, Vector and List.

We import these modules here to provide examples of their use

import qualified Data.Map as Map
import qualified Data.List as List
import qualified Data.Vector as Vector

Declare an instance of Tabulate

A record structure that will be an element in a Traversable instance. The data type has to derive from Generic and Data. Also an default instance of Tabulate is declared

data Stock = Stock {ticker::String, price::Double, marketCap::Double} deriving (Data, G.Generic)
instance T.Tabulate Stock

Sample Data

yahoo =  Stock {ticker="YHOO", price=42.29101010, marketCap=40e9}
google = Stock {ticker="GOOG", price=774.210101, marketCap=532.09e9}
amazon = Stock {ticker="AMZN", price=799.161717, marketCap=378.86e9}
-- List of records
tickers = [yahoo, google, amazon]

-- The record type 'Stock' can also be in a Map
tickers_map = Map.fromList [(10, yahoo), (100, google), (1000, amazon)]

-- Or in a Vector
tickers_vector = Vector.fromList tickers

Printing the table

 putStrLn "\nElements in a List, with records fields as column names\n"
 T.ppTable tickers

 putStrLn "\nElement in a map, with Key as first column\n"
 T.ppTable tickers_map

 putStrLn "\nElement in a Vector\n"
 T.ppTable tickers_vector

Complete Example

-- ./Example.hs
:set -XDeriveGeneric
:set -XDeriveDataTypeable

import qualified GHC.Generics as G
import Data.Data

import qualified Text.PrettyPrint.Tabulate as T
import qualified Data.Map as Map
import qualified Data.List as List
import qualified Data.Vector as Vector


data Stock = Stock {ticker::String, price::Double, marketCap::Double} deriving (Data, G.Generic)
instance T.Tabulate Stock

let yahoo =  Stock {ticker="YHOO", price=42.29101010, marketCap=40e9}
let google = Stock {ticker="GOOG", price=774.210101, marketCap=532.09e9}
let amazon = Stock {ticker="AMZN", price=799.161717, marketCap=378.86e9}


-- List of records
let tickers = [yahoo, google, amazon]

-- The record type 'Stock' can also be in a Map
let tickers_map = Map.fromList [(10, yahoo), (100, google), (1000, amazon)]

-- Or in a Vector
let tickers_vector = Vector.fromList tickers

Output

-- Print table from List
T.ppTable tickers
ticker     price              marketCap
YHOO         42.291010100     4.000000000e10
GOOG        774.210101000     5.320900000e11

-- Print table from Map
T.ppTable tickers_map
Key      ticker     price              marketCap
10       YHOO         42.291010100     4.000000000e10
10       GOOG        774.210101000     5.320900000e11


-- Print table from Vector
T.ppTable tickers_vector
ticker     price              marketCap
YHOO         42.291010100     4.000000000e10
GOOG        774.210101000     5.320900000e11

Extending

Extending for any Traversable

Any Traversable containers can be extended to work with ppTable by implementing an instance of Tabulate

Customizing formatting

Default instances of CellValueFormatter for Int, Integer, String, Float and Double are provided. To customize formatting of any types, an specific implementation of CellValueFormatter can be provided.