Hello! Today, let me show three small but interesting things that you might skip when reading the documentation to the Raku programming language (if you did read it :-).
There is a pair of transliteration (or transformation) operators in Raku:
TR. As you may guess from the name, they have something in common. But there are also some differences.
The lower case
tr performs an in-place substitution:
my $s = 'Hello, World!'; $s ~~ tr/o/ó/; say $s; # Helló, Wórld!
The target string is updated after the operation.
TR does not change the string and returns the new string as a result.
my $s = 'Hello, World!'; my $r = TR/o/ó/ with $s; say $s; # Hello, World! say $r; # Helló, Wórld!
Note that you cannot simply write
my $r = $s ~~ TR/o/ó/, but instead you need to set the topic first, for example, using
with. You can do the same with the lowercase version, too:
tr/o/ó/, .say with $s; # Helló, Wórld!
OK, what happens if you save the result of matching with
tr as in the following snippet?
my $s = 'Hello, World!'; my $r = $s ~~ tr/o/ó/;
Unlike the probable expectation, you do not simply get the new string in
$r. The type of that object is
say $r.WHAT; # (StrDistance)
When being coerced to a string, it gives you the string—the modified string after the replacement in our case. When it is coerced to an integer, you get the number of replacements happened:
say ~$r; # Helló, Wórld! say +$r; # 2
The variable also keeps both original and modified versions of the string:
say $r.before; say $r.after;
The third thing to cover in this post is to see the difference between
say, when they are called with the
The difference between
say is that
put internally calls
.Str on an object, while
From the previous section, we know that if a
StrDistance is converted to a string, it gives a string, so in our example, you see the updated string after the transliteration:
put $r; # Helló, Wórld!
say, you see more details about the contents:
say $r; # StrDistance.new(before => "Hello, World!", after => "Helló, Wórld!")