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Acaccia's solution

to Bracket Push in the PureScript Track

Published at Apr 06 2020 · 0 comments
Instructions
Test suite
Solution

Given a string containing brackets [], braces {} and parentheses (), verify that all the pairs are matched and nested correctly.

Source

Ginna Baker

Submitting Incomplete Solutions

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Main.purs

module Test.Main where

import Prelude

import Effect (Effect)
import Test.Unit.Assert as Assert
import Test.Unit (TestSuite, suite, test)
import Test.Unit.Main (runTest)
import BracketPush (isPaired)

main :: Effect Unit
main = runTest suites

suites :: TestSuite
suites = do
  suite "BracketPush.isPaired" do

    test "paired square brackets" $
      Assert.equal true
                   (isPaired "[]")

    test "empty string" $
      Assert.equal true
                   (isPaired "")

    test "unpaired brackets" $
      Assert.equal false
                   (isPaired "[[")

    test "wrong ordered brackets" $
      Assert.equal false
                   (isPaired "}{")

    test "paired with whitespace" $
      Assert.equal true
                   (isPaired "{ }")

    test "simple nested brackets" $
      Assert.equal true
                   (isPaired "{[]}")

    test "several paired brackets" $
      Assert.equal true
                   (isPaired "{}[]")

    test "paired and nested brackets" $
      Assert.equal true
                   (isPaired "([{}({}[])])")

    test "unopened closing brackets" $
      Assert.equal false
                   (isPaired "{[)][]}")

    test "unpaired and nested brackets" $
      Assert.equal false
                   (isPaired "([{])")

    test "paired and wrong nested brackets" $
      Assert.equal false
                   (isPaired "[({]})")

    test "math expression" $
      Assert.equal true
                   (isPaired "(((185 + 223.85) * 15) - 543)/2")

    test "complex latex expression" $
      Assert.equal true
                   (isPaired "\\left(\\begin{array}{cc} \\frac{1}{3} & x\\\\ \\mathrm{e}^{x} &... x^2 \\end{array}\\right)")
module BracketPush
  ( isPaired
  ) where

import Prelude

import Data.List (List(..), fromFoldable, null, (:))
import Data.String.CodeUnits (toCharArray)

data Bracket = Bracket | Brace | Parenthese
derive instance eqBracket :: Eq Bracket

isPaired :: String -> Boolean
isPaired = go Nil <<< fromFoldable <<< toCharArray
  where
    go acc Nil = null acc
    go acc ('[': xs) = go (Bracket : acc) xs
    go acc ('{': xs) = go (Brace : acc) xs
    go acc ('(': xs) = go (Parenthese : acc) xs
    go (a:acc) (']':xs) = a == Bracket && go acc xs
    go (a:acc) ('}':xs) = a == Brace && go acc xs
    go (a:acc) (')':xs) = a == Parenthese && go acc xs
    go acc (_:xs) = go acc xs

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