| Server IP : 85.214.239.14 / Your IP : 18.119.163.69 Web Server : Apache/2.4.62 (Debian) System : Linux h2886529.stratoserver.net 4.9.0 #1 SMP Tue Jan 9 19:45:01 MSK 2024 x86_64 User : www-data ( 33) PHP Version : 7.4.18 Disable Function : pcntl_alarm,pcntl_fork,pcntl_waitpid,pcntl_wait,pcntl_wifexited,pcntl_wifstopped,pcntl_wifsignaled,pcntl_wifcontinued,pcntl_wexitstatus,pcntl_wtermsig,pcntl_wstopsig,pcntl_signal,pcntl_signal_get_handler,pcntl_signal_dispatch,pcntl_get_last_error,pcntl_strerror,pcntl_sigprocmask,pcntl_sigwaitinfo,pcntl_sigtimedwait,pcntl_exec,pcntl_getpriority,pcntl_setpriority,pcntl_async_signals,pcntl_unshare, MySQL : OFF | cURL : OFF | WGET : ON | Perl : ON | Python : ON | Sudo : ON | Pkexec : OFF Directory : /proc/self/root/usr/share/doc/libparse-recdescent-perl/examples/ |
Upload File : |
#!/usr/bin/perl -ws
# THE COMMONEST REASON FOR WANTING LEFT RECURSION
use strict;
use Parse::RecDescent; $::RD_HINT = 1;
sub Parse::RecDescent::evalop {
$_[0][0] = $_[0][$_+1](@{$_[0]}[0,$_+2])
for map 2*($_-1), 1..@{$_[0]}/2;
return $_[0][0];
}
my $parse = Parse::RecDescent->new(<<'EndGrammar');
main: expr /\Z/ { $item[1] }
| <error>
expr: <leftop:term add_op term>
{ evalop($item[1]) }
add_op: '+' { sub { $_[0] += $_[1] } }
| '-' { sub { $_[0] -= $_[1] } }
term: <leftop:factor mult_op factor>
{ evalop($item[1]) }
mult_op: '*' { sub { $_[0] *= $_[1] } }
| '/' { sub { $_[0] /= $_[1] } }
factor: number
| '(' expr ')' { $item[2] }
number: /[-+]?\d+(\.\d+)?/
EndGrammar
while (<DATA>) {
print "$_ = ", $parse->main($_), "\n";
}
while (print "> " and defined($_=<>)) {
print "= ", $parse->main($_), "\n";
}
__DATA__
2+3
2*3
+1-1+1-1+1-1+1-1+1
7*7-6*8
121/(121/11)/121*11
1/(10-1/(1/(10-1)))