Parrot - Branches

Code gets a little boring without flow control; for starters, Parrot knows about branching and labels. The branch op is equivalent to Perl's goto:

         branch TERRY
JOHN:    print "fjords\n"
         branch END
MICHAEL: print " pining"
         branch GRAHAM
TERRY:   print "It's"
         branch MICHAEL
GRAHAM:  print " for the "
         branch JOHN
END:     end

It can also perform simple tests to see whether a register contains a true value:

         set I1, 12
         set I2, 5
         mod I3, I2, I2
         if I3, REMAIND, DIVISOR
REMAIND: print "5 divides 12 with remainder "
         print I3
         branch DONE
DIVISOR: print "5 is an integer divisor of 12"

DONE:    print "\n"

Here's what that would look like in Perl, for comparison:

$i1 = 12;
$i2 = 5;
$i3 = $i1 % $i2;

if ($i3) {
   print "5 divides 12 with remainder ";
   print $i3;
} else {
   print "5 is an integer divisor of 12";

print "\n";

Parrot Operator

We have the full range of numeric comparators: eq, ne, lt, gt, le and ge. Note that you can't use these operators on arguments of disparate types; you may even need to add the suffix _i or _n to the op, to tell it what type of argument you are using, although the assembler ought to divine this for you, by the time you read this.

Kickstart Your Career

Get certified by completing the course

Get Started