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marryton007's solution

to Matching Brackets in the OCaml Track

Published at Apr 21 2020 · 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.

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  1. Install the Exercism CLI.

  2. Install OCaml.

  3. For library documentation, follow Useful OCaml resources.

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make

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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)
open Base

let update stack c =
  let push c = Result.return (c :: stack) in
  let pop c =
    let (=) = Char.(=) in
    match stack with
    | (c' :: stack) when c' = c -> Result.return stack
    | _ -> Result.fail c
  in
  match c with
  | '{' -> push '}'
  | '[' -> push ']'
  | '(' -> push ')'
  | ')' | ']' | '}' -> pop c
  | _ -> Result.return stack


let are_balanced s =
  String.fold_result s ~init:[] ~f:update  |> function
  | Ok [] -> true
  | _ -> false

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