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Published at Aug 25 2019
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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.

Make sure you have read D page on exercism.io. This covers the basic information on setting up the development environment expected by the exercises.

Get the first test compiling, linking and passing by following the three rules of test-driven development. Create just enough structure by declaring namespaces, functions, classes, etc., to satisfy any compiler errors and get the test to fail. Then write just enough code to get the test to pass. Once you've done that, uncomment the next test by moving the following line past the next test.

```
static if (all_tests_enabled)
```

This may result in compile errors as new constructs may be invoked that you haven't yet declared or defined. Again, fix the compile errors minimally to get a failing test, then change the code minimally to pass the test, refactor your implementation for readability and expressiveness and then go on to the next test.

Try to use standard D facilities in preference to writing your own low-level algorithms or facilities by hand. DRefLanguage and DReference are references to the D language and D standard library.

Ginna Baker

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

```
module matching_brackets;
unittest
{
immutable int allTestsEnabled = 0;
// Paired square brackets
assert(isPaired("[]"));
static if (allTestsEnabled)
{
// Empty string
assert(isPaired(""));
// Unpaired brackets
assert(!isPaired("[["));
// Wrong ordered brackets
assert(!isPaired("}{"));
// Wrong closing bracket
assert(!isPaired("{]"));
// Paired with whitespace
assert(isPaired("{ }"));
// Partially paired brackets
assert(!isPaired("{[])"));
// Simple nested brackets
assert(isPaired("{[]}"));
// Several paired brackets
assert(isPaired("{}[]"));
// Paired and nested brackets
assert(isPaired("([{}({}[])])"));
// Unopened closing brackets
assert(!isPaired("{[)][]}"));
// Unpaired and nested brackets
assert(!isPaired("([{])"));
// Paired and wrong nested brackets
assert(!isPaired("[({]})"));
// Paired and incomplete brackets
assert(!isPaired("{}["));
// Too many closing brackets
assert(!isPaired("[]]"));
// Math expression
assert(isPaired("(((185 + 223.85) * 15) - 543)/2"));
// Complex latex expression
assert(isPaired(
"\\left(\\begin{array}{cc} \\frac{1}{3} & x\\\\ \\mathrm{e}^{x} &... x^2 \\end{array}\\right)"));
}
}
```

```
module matching_brackets;
import std.meta : aliasSeqOf;
immutable leftBrackets = "([{";
immutable rightBrackets = ")]}";
immutable bracketAliasSeq = aliasSeqOf!(leftBrackets ~ rightBrackets);
immutable leftBracketAliasSeq = aliasSeqOf!(leftBrackets);
bool isPaired(string input)
{
import std.algorithm.comparison : among;
import std.algorithm.iteration : filter;
import std.range : empty;
import std.string : indexOf;
dchar[] stack;
foreach (character; input.filter!(c => c.among(bracketAliasSeq)))
{
if (character.among(leftBracketAliasSeq))
stack.assumeSafeAppend ~= rightBrackets[leftBrackets.indexOf(character)];
else if (stack.empty)
return false;
else if (character == stack[$ - 1])
stack.length = stack.length - 1;
else
return false;
}
return stack.empty;
}
unittest
{
// Paired square brackets
assert(isPaired("[]"));
// Empty string
assert(isPaired(""));
// Unpaired brackets
assert(!isPaired("[["));
// Wrong ordered brackets
assert(!isPaired("}{"));
// Wrong closing bracket
assert(!isPaired("{]"));
// Paired with whitespace
assert(isPaired("{ }"));
// Partially paired brackets
assert(!isPaired("{[])"));
// Simple nested brackets
assert(isPaired("{[]}"));
// Several paired brackets
assert(isPaired("{}[]"));
// Paired and nested brackets
assert(isPaired("([{}({}[])])"));
// Unopened closing brackets
assert(!isPaired("{[)][]}"));
// Unpaired and nested brackets
assert(!isPaired("([{])"));
// Paired and wrong nested brackets
assert(!isPaired("[({]})"));
// Paired and incomplete brackets
assert(!isPaired("{}["));
// Too many closing brackets
assert(!isPaired("[]]"));
// Math expression
assert(isPaired("(((185 + 223.85) * 15) - 543)/2"));
// Complex latex expression
assert(isPaired(
"\\left(\\begin{array}{cc} \\frac{1}{3} & x\\\\ \\mathrm{e}^{x} &... x^2 \\end{array}\\right)"));
}
```

A huge amount can be learned from reading other peopleâ€™s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

- What compromises have been made?
- Are there new concepts here that you could read more about to improve your understanding?

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