/usr/share/doc/libparse-recdescent-perl/examples/demo_parsetree.pl is in libparse-recdescent-perl 1.967009+dfsg-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 | #!/usr/bin/perl -sw
# PARSE LOGICAL EXPRESSIONS TO A "list of lists" PARSE TREE
sub printtree
{
print " " x $_[0];
print "$_[1]:\n";
foreach ( @_[2..$#_] )
{
if (ref($_)) { printtree($_[0]+1,@$_); }
else { print " " x $_[0], "$_\n" }
}
print "\n";
}
use Parse::RecDescent;
$RD_AUTOACTION = q{ [@item] };
$grammar =
q{
expr : disj
disj : conj 'or' disj | conj
conj : unary 'and' conj | unary
unary : 'not' atom
| '(' expr ')'
| atom
atom : /[a-z]+/i
};
$parse = new Parse::RecDescent ($grammar);
while (<DATA>)
{
my $tree = $parse->expr($_);
printtree(0,@$tree) if $tree;
}
__DATA__
a and b and not c
(c or d) and f
|