Add reverse-string exercise (#703)

* Add reverse-string exercise. Excluding grapheme cluster tests
* allow grapheme cluster tests
* append some instructions

config.json

@@ -777,6 +777,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 1
+      },
+      {
+        "slug": "reverse-string",
+        "name": "Reverse String",
+        "uuid": "c73132d4-4f67-4085-ba17-84f38824afe1",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
       }
     ]
   },

exercises/practice/reverse-string/.docs/instructions.append.md

@@ -0,0 +1,13 @@
+# ignore
+
+## Unicode and grapheme clusters
+
+This exercise includes tests with Unicode strings that contain grapheme clusters.
+Perl's  builtin string processing functions are unsufficient to handle these strings.
+Here are a couple of resources to help you:
+
+* [Treat Unicode strings as grapheme clusters][foy]
+* [Extract by Grapheme Instead of Codepoint (regex)][christiansen]
+
+[foy]: https://www.effectiveperlprogramming.com/2011/06/treat-unicode-strings-as-grapheme-clusters/
+[christiansen]: https://www.perl.com/pub/2012/05/perlunicookbook-extract-by-grapheme-instead-of-codepoint-regex.html/

exercises/practice/reverse-string/.docs/instructions.md

@@ -0,0 +1,9 @@
+# Instructions
+
+Your task is to reverse a given string.
+
+Some examples:
+
+- Turn `"stressed"` into `"desserts"`.
+- Turn `"strops"` into `"sports"`.
+- Turn `"racecar"` into `"racecar"`.

exercises/practice/reverse-string/.docs/introduction.md

@@ -0,0 +1,5 @@
+# Introduction
+
+Reversing strings (reading them from right to left, rather than from left to right) is a surprisingly common task in programming.
+
+For example, in bioinformatics, reversing the sequence of DNA or RNA strings is often important for various analyses, such as finding complementary strands or identifying palindromic sequences that have biological significance.

exercises/practice/reverse-string/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "glennj"
+  ],
+  "files": {
+    "solution": [
+      "lib/ReverseString.pm"
+    ],
+    "test": [
+      "t/reverse-string.t"
+    ],
+    "example": [
+      ".meta/solutions/lib/ReverseString.pm"
+    ]
+  },
+  "blurb": "Reverse a given string.",
+  "source": "Introductory challenge to reverse an input string",
+  "source_url": "https://medium.freecodecamp.org/how-to-reverse-a-string-in-javascript-in-3-different-ways-75e4763c68cb"
+}

exercises/practice/reverse-string/.meta/solutions/lib/ReverseString.pm

@@ -0,0 +1,40 @@
+package ReverseString;
+
+use strict;
+use warnings;
+use experimental qw<signatures postderef postderef_qq>;
+
+use Exporter qw<import>;
+our @EXPORT_OK = qw<str_reverse>;
+
+sub str_reverse ($text) {
+    my $rev = '';
+
+    # \X matches "extended grapheme clusters"
+    my @chars = $text =~ /(\X)/g;
+
+    # the obvious boring solution
+    # $rev = reverse $text
+
+    # iterating
+    # foreach my $char (@chars) {
+    #   $rev = $char . $rev;
+    # }
+
+    # iterating tersely
+    # $rev = $_ . $rev for @chars;
+
+    # iterating functionally
+    # use List::Util qw(reduce);
+    # $rev = reduce {$b . $a} '', @chars;
+
+    # fewer iterations
+    for ( my ( $i, $j ) = ( 0, $#chars ); $i < $j; $i++, $j-- ) {
+        ( $chars[$i], $chars[$j] ) = ( $chars[$j], $chars[$i] );
+    }
+    $rev = join '', @chars;
+
+    return $rev;
+}
+
+1;

exercises/practice/reverse-string/.meta/solutions/t/reverse-string.t

@@ -0,0 +1 @@
+../../../t/reverse-string.t

exercises/practice/reverse-string/.meta/template-data.yaml

@@ -0,0 +1,50 @@
+subs: str_reverse
+
+properties:
+  reverse:
+    test: |-
+      use Data::Dmp;
+      local $Data::Dmp::OPT_STRINGIFY_NUMBERS = 1;
+      sprintf(<<'END', map {dmp($_)} $case->{input}{value}, $case->@{qw<expected description>});
+      is(
+          str_reverse(%s),
+          %s,
+          %s,
+      );
+      END
+
+example: |-
+  sub str_reverse ($text) {
+    my $rev = '';
+
+    # \X matches "extended grapheme clusters"
+    my @chars = $text =~ /(\X)/g;
+
+    # the obvious boring solution
+    # $rev = reverse $text 
+
+    # iterating
+    # foreach my $char (@chars) {
+    #   $rev = $char . $rev;
+    # }
+    
+    # iterating tersely
+    # $rev = $_ . $rev for @chars;
+
+    # iterating functionally
+    # use List::Util qw(reduce);
+    # $rev = reduce {$b . $a} '', @chars;
+
+    # fewer iterations
+    for (my ($i, $j) = (0, $#chars); $i < $j; $i++, $j--) {
+      ($chars[$i], $chars[$j]) = ($chars[$j], $chars[$i]);
+    }
+    $rev = join '', @chars;
+
+    return $rev;
+  }
+
+stub: |-
+  sub str_reverse ($text) {
+      return undef;
+  }

exercises/practice/reverse-string/.meta/tests.toml

@@ -0,0 +1,37 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[c3b7d806-dced-49ee-8543-933fd1719b1c]
+description = "an empty string"
+
+[01ebf55b-bebb-414e-9dec-06f7bb0bee3c]
+description = "a word"
+
+[0f7c07e4-efd1-4aaa-a07a-90b49ce0b746]
+description = "a capitalized word"
+
+[71854b9c-f200-4469-9f5c-1e8e5eff5614]
+description = "a sentence with punctuation"
+
+[1f8ed2f3-56f3-459b-8f3e-6d8d654a1f6c]
+description = "a palindrome"
+
+[b9e7dec1-c6df-40bd-9fa3-cd7ded010c4c]
+description = "an even-sized word"
+
+[1bed0f8a-13b0-4bd3-9d59-3d0593326fa2]
+description = "wide characters"
+
+[93d7e1b8-f60f-4f3c-9559-4056e10d2ead]
+description = "grapheme cluster with pre-combined form"
+
+[1028b2c1-6763-4459-8540-2da47ca512d9]
+description = "grapheme clusters"

exercises/practice/reverse-string/lib/ReverseString.pm

@@ -0,0 +1,12 @@
+package ReverseString;
+
+use v5.40;
+
+use Exporter qw<import>;
+our @EXPORT_OK = qw<str_reverse>;
+
+sub str_reverse ($text) {
+    return undef;
+}
+
+1;

exercises/practice/reverse-string/t/reverse-string.t

@@ -0,0 +1,63 @@
+#!/usr/bin/env perl
+use Test2::V0;
+
+use FindBin qw<$Bin>;
+use lib "$Bin/../lib", "$Bin/../local/lib/perl5";
+
+use ReverseString qw<str_reverse>;
+
+is( # begin: c3b7d806-dced-49ee-8543-933fd1719b1c
+    str_reverse(""),
+    "",
+    "an empty string",
+); # end: c3b7d806-dced-49ee-8543-933fd1719b1c
+
+is( # begin: 01ebf55b-bebb-414e-9dec-06f7bb0bee3c
+    str_reverse("robot"),
+    "tobor",
+    "a word",
+); # end: 01ebf55b-bebb-414e-9dec-06f7bb0bee3c
+
+is( # begin: 0f7c07e4-efd1-4aaa-a07a-90b49ce0b746
+    str_reverse("Ramen"),
+    "nemaR",
+    "a capitalized word",
+); # end: 0f7c07e4-efd1-4aaa-a07a-90b49ce0b746
+
+is( # begin: 71854b9c-f200-4469-9f5c-1e8e5eff5614
+    str_reverse("I'm hungry!"),
+    "!yrgnuh m'I",
+    "a sentence with punctuation",
+); # end: 71854b9c-f200-4469-9f5c-1e8e5eff5614
+
+is( # begin: 1f8ed2f3-56f3-459b-8f3e-6d8d654a1f6c
+    str_reverse("racecar"),
+    "racecar",
+    "a palindrome",
+); # end: 1f8ed2f3-56f3-459b-8f3e-6d8d654a1f6c
+
+is( # begin: b9e7dec1-c6df-40bd-9fa3-cd7ded010c4c
+    str_reverse("drawer"),
+    "reward",
+    "an even-sized word",
+); # end: b9e7dec1-c6df-40bd-9fa3-cd7ded010c4c
+
+is( # begin: 1bed0f8a-13b0-4bd3-9d59-3d0593326fa2
+    str_reverse("\x{5B50}\x{732B}"),
+    "\x{732B}\x{5B50}",
+    "wide characters",
+); # end: 1bed0f8a-13b0-4bd3-9d59-3d0593326fa2
+
+is( # begin: 93d7e1b8-f60f-4f3c-9559-4056e10d2ead
+    str_reverse("Wu\x{308}rstchenstand"),
+    "dnatsnehctsru\x{308}W",
+    "grapheme cluster with pre-combined form",
+); # end: 93d7e1b8-f60f-4f3c-9559-4056e10d2ead
+
+is( # begin: 1028b2c1-6763-4459-8540-2da47ca512d9
+    str_reverse("\x{E1C}\x{E39}\x{E49}\x{E40}\x{E02}\x{E35}\x{E22}\x{E19}\x{E42}\x{E1B}\x{E23}\x{E41}\x{E01}\x{E23}\x{E21}"),
+    "\x{E21}\x{E23}\x{E01}\x{E41}\x{E23}\x{E1B}\x{E42}\x{E19}\x{E22}\x{E02}\x{E35}\x{E40}\x{E1C}\x{E39}\x{E49}",
+    "grapheme clusters",
+); # end: 1028b2c1-6763-4459-8540-2da47ca512d9
+
+done_testing;