PureScript by Example - 6.3 Show Me! - Exercise 1 Solution

ShowMe.purs

module ShowMe where

import Prelude

-- Utilities from https://github.com/paf31/purescript-book/blob/master/exercises/chapter5/src/Data/Picture.purs
-- required to complete this exercise

data Point = Point
  { x :: Number
  , y :: Number
  }

showPoint :: Point -> String
showPoint (Point { x, y }) =
  "(" <> show x <> ", " <> show y <> ")"

data Shape
  = Circle Point Number
  | Rectangle Point Number Number
  | Line Point Point
  | Text Point String

showShape :: Shape -> String
showShape (Circle c r) =
  "Circle [center: " <> showPoint c <> ", radius: " <> show r <> "]"
showShape (Rectangle c w h) =
  "Rectangle [center: " <> showPoint c <> ", width: " <> show w <> ", height: " <> show h <> "]"
showShape (Line start end) =
  "Line [start: " <> showPoint start <> ", end: " <> showPoint end <> "]"
showShape (Text loc text) =
  "Text [location: " <> showPoint loc <> ", text: " <> show text <> "]"

-- Just for the sake of completeness ...
instance showPoint' :: Show Point where
  show = showPoint

-- Exercise 1
instance showShape' :: Show Shape where
  show = showShape