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# erszcz's solution

## to Bracket Push in the PureScript Track

Published at Jul 13 2018 · 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" $Assert.equal true (isPaired "\\left(\\begin{array}{cc} \\frac{1}{3} & x\\\\ \\mathrm{e}^{x} &... x^2 \\end{array}\\right)") module BracketPush ( isPaired ) where import Prelude import Data.List (List(..), (:), fromFoldable) import Data.String (toCharArray) isPaired expr = isPaired' (fromFoldable$ toCharArray expr) Nil
where
isPaired' Nil Nil = true
isPaired' Nil _ = false
isPaired' (']':_) ( s :stack) | s /= '[' = false
isPaired' ('}':_) ( b :stack) | b /= '{' = false
isPaired' (')':_) ( p :stack) | p /= '(' = false
isPaired' (']':e) ('[':stack) = isPaired' e stack
isPaired' ('}':e) ('{':stack) = isPaired' e stack
isPaired' (')':e) ('(':stack) = isPaired' e stack
isPaired' ('[':e) stack = isPaired' e ('[':stack)
isPaired' ('{':e) stack = isPaired' e ('{':stack)
isPaired' ('(':e) stack = isPaired' e ('(':stack)
isPaired' ( c :e) stack = isPaired' e stack