To further reduce the syntax burden, we can eliminate many calls to the text constructor by letting element constructors accept an optional third argument for text content. In the common case, we no longer have need to call text. (Of course, should we want to call text for clarity, we still can.)

For example, the following fragment:

html {
    head { title { text "Title" } };
    body {
        p { class_ "warning"; text "paragraph" }
    }
};

[download]
can be simplified to this: 
html {
    head { title {} "Title" };
    body {
        p { class_ "warning" } "paragraph"
    }
};

[download]

To effect the new syntax rules, we need only change the _elem and define_vocabulary functions from our original implementation. The changes are simple and marked with a hash-bang (#!):

sub _elem {
    my ($elem_name, $content_fn, $text) = @_;   #! added $text arg
    # an element is represented by the triple [name, attrs, children]
    my $elem = [$elem_name, undef, undef];
    do { local $__frag = $elem;
         $content_fn->();              
         text($text) if defined $text;          #! new line
    };
    push @{$__frag->[2]}, $elem;
}

sub define_vocabulary {
    my ($elems, $attrs) = @_;
    eval "sub $_(&@) { _elem('$_',\@_) }"    for @$elems;  #! proto
    eval "sub ${_}_(\$) { _attr('$_',\@_) }" for @$attrs;
}

[download]

Can you spot any other syntax-reduction opportunities?

Cheers,
Tom

Tom Moertel : Blog / Talks / CPAN / LectroTest / PXSL / Coffee / Movie Rating Decoder

In reply to Simplifying the syntax further by tmoertel
in thread Embedding a mini-language for XML construction into Perl by tmoertel

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