All your html/xml elements take a code-block as *{$_} = sub(&) { _elem($name, @_) }; and should per default memorize the result and return the pre-calculated result.

How would you do that? In the anonsub, I can inspect @_, but how would you determine what _elem() returns, without that subroutine being called? I can't think of a way to tell whether the codepath is entirely static.

But memoizing should be done per DTD inside HTML::Writer, so import() doesn't do the DTD parsing again and again.

The most obvious solution is to use a package , something like ...

TIMTOWTDI. The prescripted usage could be 

package Test;
my $foo  = "my \$foo";
our $bar = "our \$bar";
my $pack = __PACKAGE__;

sub baz { "$_[0] called Test::baz" }

package Page {
    use HTML::Writer qw(xhtml1-transitional.dtd);
    push local @ISA, $pack;
    render {
        HTML {
            HEAD {
                TITLE { "foo bar"};
            };
            BODY {
                class_ "ugly";
                onload_ "javascript: mumble()";
                DIV {
                    class_ "foo";
                    id_    "bar";
                    t      "If in doubt, mumble.";
                    IMG { src_ "foo.jpg" };
                };
                TABLE {
                    my $c;
                    for ($foo, $bar, Page->baz) {
                        TR {
                            TD { $_ }; TD { $c++};
                        }
                    }
                };
                DIV { class_ "bar"; t "End of that." };
            }
        };
    };
};

[download]

which constrains the DSL symbols to the Page package, whilst having the outer context visible.

Other ways are possible, of course. More thinking required.

The re-evaling would introduce yet more overhead, see 1) performance...

update: in the above example, in package Test there is my $pack = __PACKAGE__;. Is there a way to get at the name of the lexically surrounding package inside package Page ?

perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'

In reply to Re^5: Which internal DSL are there in Perl? (Domain Specific Languages - Part 1) by shmem
in thread Which internal DSL are there in Perl? (Domain Specific Languages - Part 1) by LanX

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