Another article of the series “Yet Another Perl 6 Operator”
Today’s operator is a very simple one, the string concatenation operator.
my $a = 'ab' ~ 'c'; # 'abc' my $b = 'def'; my $c = $a ~ $b; # 'abcdef'
The operator is now written
'~' and not
'.' as in Perl 5. Think of it as “stitching” the two ends of its arguments together (S03).
Appending to a string can likewise be done with
'~='. (Compare to
'+=' that adds to a number.)
$c ~= "xyz"; # 'abcdefxyz' my $d = $a; $d ~= $b; # 'abcdef'
The infix operator
'~' keeps the same precedence as
'+' in Perl 6. The tilde is consistently employed for string operations and fits nicely with the unary
'~' that coerces its argument to strings and the prefix
'~' (used in operators like
'~|') to mean bitwise operations on arguments interpreted as long bit strings.
String interpolation is still built on terms of string concatenation, meaning
"Answer = $answer\n" is equivalent to
'Answer = ' ~ $answer ~ "\n".
The compatibily break with Perl 5 was a rather important one, since
'.' was after a few years of common OO practice the operator of choice to join together the invocant object and a member (attribute, method, etc.). The repurposing was a long awaited thing.
At the other hand, in Perl 5,
'~' is no longer the bitwise not. If you look closer to Perl 6 design, you’ll see it is filled with these breaks with traditions for the sake of a greater cause: consistency.
Friday (September 21, 2007) will bring you the next article of the series.
More thanks to the folks at #perl6 (at irc.freenode.net) and at the email@example.com mailing list.