Given a string containing brackets []
, braces {}
, parentheses ()
,
or any combination thereof, verify that any and all pairs are matched
and nested correctly.
For library documentation, follow Useful OCaml resources.
A Makefile
is provided with a default target to compile your solution and run the tests. At the command line, type:
make
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Ginna Baker
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 "[({]})");
"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)
val are_balanced : string -> bool
open Core
let are_balanced s =
let stack = Stack.create ()
in
let process_close exp =
match Stack.top stack with
| Some(x) when x = exp ->
let _ = Stack.pop stack in
true
| _ -> false
in
String.to_list s
|> List.fold
~init: true
~f: (fun res ch ->
match ch with
| '(' | '{' | '[' -> Stack.push stack ch; res
| ')' -> res && process_close '('
| '}' -> res && process_close '{'
| ']' -> res && process_close '['
| _ -> res
)
|> fun x -> x && Stack.is_empty stack
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