This is a question regarding HTML::Template::Expr. I have a template which has a big tmpl_loop block. And inside there are lot of tmpl_vars and tmpl_ifs with expr attributes. They expr attribute values(expressions) just have the ||, &&, ==, <, ( and ) symbols. I also added a function "not" which is nothing but sub { !shift }.

The problem was that it was taking about 6 seconds for the template output() call when the tmpl_loop got around 130 records! So I tried to implement differently. I used the following code to convert the template text so that it can be filled with HTML::Template.

    my $template_text = read_file('test.tmpl');
    # get all expr attributes
    my @orig_exprs = ($template_text =~ /expr="[^"]*"/g);
    my @exprs = @orig_exprs;

    @exprs = map({s/\s+//g; s/^expr="//; s/"$//; s/not\((.*?)\)/!$1/g;
+ $_} @exprs);

    @orig_exprs = map({s/[|&()]/\\$&/g; $_} @orig_exprs);

    # construct new tmpl_var/tmpl_if names in place of the expressions
    my @expr_names = @exprs;
    @expr_names = map({s/==/_is_/g; s/</_lt_/g; s/\|\|/_or_/g; s/\&\&/
+_and_/g;
                       s/!/not_/g; $_} @expr_names);

    # replace the expression names in the actual template
    $template_text =~ s/$orig_exprs[$_]/$expr_names[$_]/g for ( 0..$#e
+xprs );

    @exprs = map({s/\w{2,}/\$row->\{$&\}/g; $_} @exprs);

    # generate new template file
    my $tmpl_filename = '/tmp/test.tmpl');
    write_file($tmpl_filename, $template_text);

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And here is the function that was used to set the values for the new expression variables in the template. 
sub _fill_expr_params {
    my ($row, $expr_names, $exprs) = @_;
    $row->{$expr_names->[$_]} = eval($exprs->[$_]) for ( 0.. $#$exprs 
+);
}

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A hash-ref for a record $row with template variables used in the expresssion will be passed to this function and the references of @expr_names and @exprs arrays that we saw earlier will be paseed in to this function.

After doing this conversion I found that it took just 1 second for the template output() call! And I checked whether it works fine and it did. Can anyone please suggest whether I am making any mistake here? I saw in HTML::Template::Expr that Parse::RecDescent was used for evaluating expressions but in my _fill_expr_params function I have just used eval. Can this cause any problem?

Although I haven't done some optimizations yet like registering the functions beforehand(http://search.cpan.org/~samtregar/HTML-Template-Expr-0.07/Expr.pm#MOD_PERL_TIP) I think it shouldn't make much of a difference in the template output. Please correct me if I am wrong.

Thanks,
Ganesh

In reply to Optimize a HTML::Template::Expr template by ganeshk

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