Exporting of dynamically scoped variables?
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5
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Basically, the question is more about grammars but I think that it could be more of a interesting exercise on dynamic variables.
I have a grammar role with a prototyped token (the example is simplified to demonstrate the idea):
proto token foo {*}
token foo:sym<a> {
:my $*delimiter = q<">;
" ~ " <value>
}
token foo:sym<b> {
:my $*delimiter = q<'>;
' ~ ' <value>
}
token value {
.+? <?before $($*delimeter) || $($*custom-delimiter)>
}
When the role is consumed by a grammar I want the $*custom-delimiter to be set by the grammar. Of course, I can declare it everywhere where <foo> is needed. But sometimes it is ok to have it pre-initialized with a universal default. Something like:
{ $*custom-delimiter //= $default-delimiter }
in the value token would work. But external pre-declaration would still be needed.
I hoped that:
our $*custom-delimiter is export = $default-delimiter;
in the scope of module where the role is declared would work. But apparently it doesn't. So, the question is: are there any elegant solutions to this?
Actually, I also hope that the solution would allow to move declaration of $*delimiter in foo outside of the token definitions too.
As a side note: my first thought was about adding a parameter to the token. But having absolutely identical signatures for each variant is looking terrible too:
token foo:sym<a> ( $*custom-delimiter = $default-delimiter ) {
}
token foo:sym<b> ( $*custom-delimiter = $default-delimiter ) {
}
token foo:sym<c> ( $*custom-delimiter = $default-delimiter ) {
}
Another approach is to have something like:
token pre-foo ( $*custom-delimiter = $default-delimiter ) {
<foo>
}
In this case an additional method would be required in actions class to propagate $/<foo>.ast one level up.
perl6
asked Nov 15 at 19:22
Vadim Belman
40612
add a comment |
up vote
5
down vote
favorite
Basically, the question is more about grammars but I think that it could be more of a interesting exercise on dynamic variables.
I have a grammar role with a prototyped token (the example is simplified to demonstrate the idea):
proto token foo {*}
token foo:sym<a> {
:my $*delimiter = q<">;
" ~ " <value>
}
token foo:sym<b> {
:my $*delimiter = q<'>;
' ~ ' <value>
}
token value {
.+? <?before $($*delimeter) || $($*custom-delimiter)>
}
When the role is consumed by a grammar I want the $*custom-delimiter to be set by the grammar. Of course, I can declare it everywhere where <foo> is needed. But sometimes it is ok to have it pre-initialized with a universal default. Something like:
{ $*custom-delimiter //= $default-delimiter }
in the value token would work. But external pre-declaration would still be needed.
I hoped that:
our $*custom-delimiter is export = $default-delimiter;
in the scope of module where the role is declared would work. But apparently it doesn't. So, the question is: are there any elegant solutions to this?
Actually, I also hope that the solution would allow to move declaration of $*delimiter in foo outside of the token definitions too.
As a side note: my first thought was about adding a parameter to the token. But having absolutely identical signatures for each variant is looking terrible too:
token foo:sym<a> ( $*custom-delimiter = $default-delimiter ) {
}
token foo:sym<b> ( $*custom-delimiter = $default-delimiter ) {
}
token foo:sym<c> ( $*custom-delimiter = $default-delimiter ) {
}
Another approach is to have something like:
token pre-foo ( $*custom-delimiter = $default-delimiter ) {
<foo>
}
In this case an additional method would be required in actions class to propagate $/<foo>.ast one level up.
perl6
asked Nov 15 at 19:22
Vadim Belman
40612
1
I'm too tired to be able to understand your question tonight. But you know roles can be parameterized, right? egrole foo[$bar = 99] { method baz { say $bar } }; foo[42].baz; # 42. Is that relevant?
– raiph
Nov 16 at 2:45
Never needed it, so – it's a good reminder! But – no, unfortunately. Tokenfoois used by the same grammar in different contexts where different delimiters are used.
– Vadim Belman
Nov 16 at 2:49
add a comment |
up vote
5
down vote
favorite
up vote
5
down vote
favorite
Basically, the question is more about grammars but I think that it could be more of a interesting exercise on dynamic variables.
I have a grammar role with a prototyped token (the example is simplified to demonstrate the idea):
proto token foo {*}
token foo:sym<a> {
:my $*delimiter = q<">;
" ~ " <value>
}
token foo:sym<b> {
:my $*delimiter = q<'>;
' ~ ' <value>
}
token value {
.+? <?before $($*delimeter) || $($*custom-delimiter)>
}
When the role is consumed by a grammar I want the $*custom-delimiter to be set by the grammar. Of course, I can declare it everywhere where <foo> is needed. But sometimes it is ok to have it pre-initialized with a universal default. Something like:
{ $*custom-delimiter //= $default-delimiter }
in the value token would work. But external pre-declaration would still be needed.
I hoped that:
our $*custom-delimiter is export = $default-delimiter;
in the scope of module where the role is declared would work. But apparently it doesn't. So, the question is: are there any elegant solutions to this?
Actually, I also hope that the solution would allow to move declaration of $*delimiter in foo outside of the token definitions too.
As a side note: my first thought was about adding a parameter to the token. But having absolutely identical signatures for each variant is looking terrible too:
token foo:sym<a> ( $*custom-delimiter = $default-delimiter ) {
}
token foo:sym<b> ( $*custom-delimiter = $default-delimiter ) {
}
token foo:sym<c> ( $*custom-delimiter = $default-delimiter ) {
}
Another approach is to have something like:
token pre-foo ( $*custom-delimiter = $default-delimiter ) {
<foo>
}
In this case an additional method would be required in actions class to propagate $/<foo>.ast one level up.
perl6
asked Nov 15 at 19:22
Vadim Belman
40612
Basically, the question is more about grammars but I think that it could be more of a interesting exercise on dynamic variables.
I have a grammar role with a prototyped token (the example is simplified to demonstrate the idea):
proto token foo {*}
token foo:sym<a> {
:my $*delimiter = q<">;
" ~ " <value>
}
token foo:sym<b> {
:my $*delimiter = q<'>;
' ~ ' <value>
}
token value {
.+? <?before $($*delimeter) || $($*custom-delimiter)>
}
When the role is consumed by a grammar I want the $*custom-delimiter to be set by the grammar. Of course, I can declare it everywhere where <foo> is needed. But sometimes it is ok to have it pre-initialized with a universal default. Something like:
{ $*custom-delimiter //= $default-delimiter }
in the value token would work. But external pre-declaration would still be needed.
I hoped that:
our $*custom-delimiter is export = $default-delimiter;
in the scope of module where the role is declared would work. But apparently it doesn't. So, the question is: are there any elegant solutions to this?
Actually, I also hope that the solution would allow to move declaration of $*delimiter in foo outside of the token definitions too.
As a side note: my first thought was about adding a parameter to the token. But having absolutely identical signatures for each variant is looking terrible too:
token foo:sym<a> ( $*custom-delimiter = $default-delimiter ) {
}
token foo:sym<b> ( $*custom-delimiter = $default-delimiter ) {
}
token foo:sym<c> ( $*custom-delimiter = $default-delimiter ) {
}
Another approach is to have something like:
token pre-foo ( $*custom-delimiter = $default-delimiter ) {
<foo>
}
In this case an additional method would be required in actions class to propagate $/<foo>.ast one level up.
perl6
perl6
asked Nov 15 at 19:22
Vadim Belman
40612
asked Nov 15 at 19:22
Vadim Belman
40612
asked Nov 15 at 19:22
Vadim Belman
40612
asked Nov 15 at 19:22
Vadim Belman
40612
asked Nov 15 at 19:22
Vadim Belman
40612
40612
1
I'm too tired to be able to understand your question tonight. But you know roles can be parameterized, right? egrole foo[$bar = 99] { method baz { say $bar } }; foo[42].baz; # 42. Is that relevant?
– raiph
Nov 16 at 2:45
Never needed it, so – it's a good reminder! But – no, unfortunately. Tokenfoois used by the same grammar in different contexts where different delimiters are used.
– Vadim Belman
Nov 16 at 2:49
add a comment |
1
I'm too tired to be able to understand your question tonight. But you know roles can be parameterized, right? egrole foo[$bar = 99] { method baz { say $bar } }; foo[42].baz; # 42. Is that relevant?
– raiph
Nov 16 at 2:45
Never needed it, so – it's a good reminder! But – no, unfortunately. Tokenfoois used by the same grammar in different contexts where different delimiters are used.
– Vadim Belman
Nov 16 at 2:49
1
1
I'm too tired to be able to understand your question tonight. But you know roles can be parameterized, right? eg
role foo[$bar = 99] { method baz { say $bar } }; foo[42].baz; # 42. Is that relevant?– raiph
Nov 16 at 2:45
I'm too tired to be able to understand your question tonight. But you know roles can be parameterized, right? eg
role foo[$bar = 99] { method baz { say $bar } }; foo[42].baz; # 42. Is that relevant?– raiph
Nov 16 at 2:45
Never needed it, so – it's a good reminder! But – no, unfortunately. Token
foo is used by the same grammar in different contexts where different delimiters are used.– Vadim Belman
Nov 16 at 2:49
Never needed it, so – it's a good reminder! But – no, unfortunately. Token
foo is used by the same grammar in different contexts where different delimiters are used.– Vadim Belman
Nov 16 at 2:49
add a comment |
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1
I'm too tired to be able to understand your question tonight. But you know roles can be parameterized, right? eg
role foo[$bar = 99] { method baz { say $bar } }; foo[42].baz; # 42. Is that relevant?– raiph
Nov 16 at 2:45
Never needed it, so – it's a good reminder! But – no, unfortunately. Token
foois used by the same grammar in different contexts where different delimiters are used.– Vadim Belman
Nov 16 at 2:49