Hi Patrick,
for note that this codeline:
my Str $input = "Here be a $(placeholder), for $(purpose) purposes.";
will not compile because Perl will try to interpolate $(placeholder) and
$(purpose) as vairables that have not been declared.
You need to use non interpolating quotes:
my Str $input = 'Here be a $(placeholder), for $(purpose) purposes.';
Then, I would probably use simple substitutions, as with this example:
my Str $input = 'Here be a $(placeholder), for $(purpose) purposes.';
sub format-string ($input, %substitutions) {
my $str = $input;
for keys %substitutions -> $key {
$str ~~ s/$key/%substitutions{$key}/;
}
return $str;
}
my %substitutes = '$(placeholder)' => "placeholder", '$(purpose)' =>
"testing";
my $output = format-string($input, %substitutes);
say $output;
This is the output running this under the REPL:
> my Str $input = 'Here be a $(placeholder), for $(purpose) purposes.';
Here be a $(placeholder), for $(purpose) purposes.
>
> sub format-string ($input, %substitutions) {
* my $str = $input;
* for keys %substitutions -> $key {
* $str ~~ s/$key/%substitutions{$key}/;
* }
* return $str;
* }
sub format-string ($input, %substitutions) { #`(Sub|214745424) ... }
> my %substitutes = '$(placeholder)' => "placeholder", '$(purpose)' =>
"testing";
{$(placeholder) => placeholder, $(purpose) => testing}
> my $output = format-string($input, %substitutes);
Here be a placeholder, for testing purposes.
> say $output;
Here be a placeholder, for testing purposes.
I hope this helps.
Cheers,
Laurent.
Le mar. 28 août 2018 à 12:25, Patrick Spek via perl6-users <
perl6-us...@perl.org> a écrit :
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
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> Hi all,
>
> I'm trying to substitute parts of a string, and thought this might be a
> good use of a grammar. Sadly, grammars aren't my strong suit, so I
> thought I'd ask the wider community for help. Maybe you guys know an
> even better solution than using a grammar here.
>
> So, consider a string, "Here be a $(placeholder), for $(purpose)
> purposes.". I want to be able to put that into a sub, along with some
> Pairs, and get a string with the placeholders replaced back.
>
> my Str $input = "Here be a $(placeholder), for $(purpose) purposes.";
> my Str $output = format-string(
> $input,
> placeholder => "placeholder",
> purpose => "testing",
> );
>
> dd $output; # "Here be a placeholder, for testing purposes."
>
> The `format-string` sub would call the grammar and apply the actual
> substitution, and that's where I need your help. I am not quite sure
> how I would implement the grammar (and presumably it's actions) to do
> what I want.
>
> Thanks in advance for your help!
>
> - --
> With kind regards,
>
> Patrick Spek
>
>
> www: https://www.tyil.work/
> mail: p.s...@tyil.nl
> pgp: EB9E A484 1672 2D37 16F5 A799 9ACF E193 FFBC 1F50
>
> mastodon: @tyil@mastodon.social
> github: @Tyil
> gitlab: @tyil
>
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