# objectisundefined's solution

## to Matching Brackets in the OCaml Track

Published at Dec 18 2019 · 0 comments
Instructions
Test suite
Solution

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

## Getting Started

1. For library documentation, follow Useful OCaml resources.

## Running Tests

A Makefile is provided with a default target to compile your solution and run the tests. At the command line, type:

make


## Submitting Incomplete Solutions

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

## Feedback, Issues, Pull Requests

The exercism/ocaml repository on GitHub is the home for all of the Ocaml exercises.

If you have feedback about an exercise, or want to help implementing a new one, head over there and create an issue or submit a PR. We welcome new contributors!

## Source

Ginna Baker

### test.ml

open Base
open OUnit2
open Matching_brackets

let ae exp got _test_ctxt =
assert_equal exp got ~printer:Bool.to_string

let tests = [
"paired square brackets" >::
ae true (are_balanced "[]");
"empty string" >::
ae true (are_balanced "");
"unpaired brackets" >::
ae false (are_balanced "[[");
"wrong ordered brackets" >::
ae false (are_balanced "}{");
"wrong closing bracket" >::
ae false (are_balanced "{]");
"paired with whitespace" >::
ae true (are_balanced "{ }");
"partially paired brackets" >::
ae false (are_balanced "{[])");
"simple nested brackets" >::
ae true (are_balanced "{[]}");
"several paired brackets" >::
ae true (are_balanced "{}[]");
"paired and nested brackets" >::
ae true (are_balanced "([{}({}[])])");
"unopened closing brackets" >::
ae false (are_balanced "{[)][]}");
"unpaired and nested brackets" >::
ae false (are_balanced "([{])");
"paired and wrong nested brackets" >::
ae false (are_balanced "[({]})");
"paired and incomplete brackets" >::
ae false (are_balanced "{}[");
"too many closing brackets" >::
ae false (are_balanced "[]]");
"math expression" >::
ae true (are_balanced "(((185 + 223.85) * 15) - 543)/2");
"complex latex expression" >::
ae true (are_balanced "\\left(\\begin{array}{cc} \\frac{1}{3} & x\\\\ \\mathrm{e}^{x} &... x^2 \\end{array}\\right)");
]

let () =
run_test_tt_main ("matching-brackets tests" >::: tests)
(* let are_balanced _ =
failwith "'are_balanced' is missing" *)

open Base

(* let rec is_odd = function
| 0 -> false
| n -> is_even (n-1)
and is_even = function
| 0 -> true
| n -> is_odd (n-1) *)

let are_balanced s =
let rec f acc l =
match l with
| [] -> List.is_empty acc
| x :: xs -> if Char.(x = '(' || x = '[' || x = '{' || x= ')' || x = ']' || x = '}') then g acc l else f acc xs
and g acc l =
match (acc, l) with
| ('(' :: acc', ')' :: l') -> f acc' l'
| ('[' :: acc', ']' :: l') -> f acc' l'
| ('{' :: acc', '}' :: l') -> f acc' l'
| (_, '(' :: l') -> f ('(' :: acc) l'
| (_, '[' :: l') -> f ('[' :: acc) l'
| (_, '{' :: l') -> f ('{' :: acc) l'
| _ -> false

in f [] (String.to_list s)
;;