Hi,
Searching for template libraries I found some examples in the net. When
thinking about it I came up with a own version that I'd
like to post here. It seems to me that it is the simples, and stil most powerful version
how to handle templates.
Instead of creating a own language on top of perl my version is a transformation
into perl. Creating a function that is then evaled into the current namespace. The template
creating is therefore a simple function call. The syntax elements are :
{* ... perl code *} => copy as is
[.* ... perl subblock *} => $out .= &{sub {... }}();
{* ... perl forloop start *-} ... {-* ... forloop end ... *} => transformed into a loop (real code yourself)
All other parts are transformed into a $out .= "..."; At the end $out is the functions return.
I'd like to ask: isnt everything else too much. All the library overhead you get
with all the different template libraries.
-- Greetings Konrad
--------------- template.pl ----------------
$RE_template_b_squarebrackets = qr'(?:[\[]((?:(?>[^\[\]]+)|(??{$RE_template_b_squarebrackets}))*)[\]])';
$RE_template_balanced_squarebrackets = qr'(?:\[\*((?:(?>(?:(?:(?!\[\*)(?!\*\])[\s\S]))+)|(??{$RE_template_balanced_squarebrackets}))*)\*\])';
$RE_template_balanced_brackets = qr'(?:\{\*((?:(?>(?:(?:(?!\{\*)(?!\*\})[\s\S]))+)|(??{$RE_template_balanced_brackets}))*)\*\})';
$RE_template_balanced_brackets_inner = qr'(?:\*-\}((?:(?>(?:(?:(?!\{-\*)(?!\*-\})[\s\S]))+)|(??{$RE_template_balanced_brackets_inner}))*)\{-\*)';
$a = "x
{
{* my \@a = (1,2,3);
foreach my \$a (\@a) { *-} y [* \$a *] {-* } *}
}
";
print (convert_template('::func',$a));
eval(convert_template('::func',$a));
print $@ if ($@);
print "'".func()."'";
sub convert_template {
my ($n,$a) = @_;
my $c = "";
while(length($a)) {
if ($a =~ /^$RE_template_balanced_squarebrackets/s ) {
my ($all,$b) = ($&,$1);
print ("Found '$all'\n");
$a = substr($a,length($all));
$c .= "\$out .= &{sub { $b }}();\n";
} elsif ($a =~ /^$RE_template_balanced_brackets/s ) {
my ($all,$b) = ($&,$1);
print ("Found '$all'\n");
$a = substr($a,length($all));
if ($b =~ /$RE_template_balanced_brackets_inner/) {
my ($pre,$b2,$post) = ($`,$1,substr($b,length($`.$&)));
$c .= "my \@_a = (); $pre";
$c .= "push(\@_a,&{".convert_template('',$b2)."}(\@_));\n";
$c .= $post;
$c .= "\$out .= join_template(\$out,\@_a);\n";
$a =~ s/^\s*\n//;
} else {
$c .= $b;
}
} elsif ($a =~ /^.+?(?=\{\*|\[.\*|$)/s) {
my ($all,$b) = ($&,$1);
print ("Found '$all'\n");
$a = substr($a,length($all));
$c .= "\$out .= \"$all\";\n";
} else {
die("Cant decode '$a'");
}
}
return "sub $n { my (\$out,\$self) = ('',\@_); $c; return \$out; }";
}
sub join_template {
my ($out,@a) = @_;
my $post = 0;
$post = length($1) if ($out =~ /([^\n]*)$/);
$pre = sprintf('%*s',$post,"");
my $c = join("\n", map { $_=~ s/^\s*\n//; $_=~ s/\s*\n\s*$//; $_ } @a);
$c .= "\n" if (scalar(@a));
return $c;
}
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Searching for template libraries I found some examples in the net. When
thinking about it I came up with a own version that I'd
like to post here. It seems to me that it is the simples, and stil most powerful version
how to handle templates.
Instead of creating a own language on top of perl my version is a transformation
into perl. Creating a function that is then evaled into the current namespace. The template
creating is therefore a simple function call. The syntax elements are :
{* ... perl code *} => copy as is
[.* ... perl subblock *} => $out .= &{sub {... }}();
{* ... perl forloop start *-} ... {-* ... forloop end ... *} => transformed into a loop (real code yourself)
All other parts are transformed into a $out .= "..."; At the end $out is the functions return.
I'd like to ask: isnt everything else too much. All the library overhead you get
with all the different template libraries.
-- Greetings Konrad
--------------- template.pl ----------------
$RE_template_b_squarebrackets = qr'(?:[\[]((?:(?>[^\[\]]+)|(??{$RE_template_b_squarebrackets}))*)[\]])';
$RE_template_balanced_squarebrackets = qr'(?:\[\*((?:(?>(?:(?:(?!\[\*)(?!\*\])[\s\S]))+)|(??{$RE_template_balanced_squarebrackets}))*)\*\])';
$RE_template_balanced_brackets = qr'(?:\{\*((?:(?>(?:(?:(?!\{\*)(?!\*\})[\s\S]))+)|(??{$RE_template_balanced_brackets}))*)\*\})';
$RE_template_balanced_brackets_inner = qr'(?:\*-\}((?:(?>(?:(?:(?!\{-\*)(?!\*-\})[\s\S]))+)|(??{$RE_template_balanced_brackets_inner}))*)\{-\*)';
$a = "x
{
{* my \@a = (1,2,3);
foreach my \$a (\@a) { *-} y [* \$a *] {-* } *}
}
";
print (convert_template('::func',$a));
eval(convert_template('::func',$a));
print $@ if ($@);
print "'".func()."'";
sub convert_template {
my ($n,$a) = @_;
my $c = "";
while(length($a)) {
if ($a =~ /^$RE_template_balanced_squarebrackets/s ) {
my ($all,$b) = ($&,$1);
print ("Found '$all'\n");
$a = substr($a,length($all));
$c .= "\$out .= &{sub { $b }}();\n";
} elsif ($a =~ /^$RE_template_balanced_brackets/s ) {
my ($all,$b) = ($&,$1);
print ("Found '$all'\n");
$a = substr($a,length($all));
if ($b =~ /$RE_template_balanced_brackets_inner/) {
my ($pre,$b2,$post) = ($`,$1,substr($b,length($`.$&)));
$c .= "my \@_a = (); $pre";
$c .= "push(\@_a,&{".convert_template('',$b2)."}(\@_));\n";
$c .= $post;
$c .= "\$out .= join_template(\$out,\@_a);\n";
$a =~ s/^\s*\n//;
} else {
$c .= $b;
}
} elsif ($a =~ /^.+?(?=\{\*|\[.\*|$)/s) {
my ($all,$b) = ($&,$1);
print ("Found '$all'\n");
$a = substr($a,length($all));
$c .= "\$out .= \"$all\";\n";
} else {
die("Cant decode '$a'");
}
}
return "sub $n { my (\$out,\$self) = ('',\@_); $c; return \$out; }";
}
sub join_template {
my ($out,@a) = @_;
my $post = 0;
$post = length($1) if ($out =~ /([^\n]*)$/);
$pre = sprintf('%*s',$post,"");
my $c = join("\n", map { $_=~ s/^\s*\n//; $_=~ s/\s*\n\s*$//; $_ } @a);
$c .= "\n" if (scalar(@a));
return $c;
}
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