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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.

Ginna Baker

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### 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