Add support for exit(). Simplify combine() so that it can handle exit/list interaction

[perl/modules/Sub-Nary.git] / lib / Sub / Nary.pm

diff --git a/lib/Sub/Nary.pm b/lib/Sub/Nary.pm
index 1406d6695dbde7f89ce4e62c52177c039a34cef4..73345b506a4ccfc870ab848ce6b527bf8cf74028 100644 (file)
--- a/lib/Sub/Nary.pm
+++ b/lib/Sub/Nary.pm
@@ -43,9 +43,23 @@ The usual constructor. Currently takes no argument.
 
 =head2 C<nary $coderef>
 
-Takes a code reference to a named or anonymous subroutine, and returns a hash reference whose keys are the possible numbers of returning scalars, and the corresponding values the "probability" to get them. The special key C<'list'> is used to denote a possibly infinite number of returned arguments. The return value hence would look at
+Takes a code reference to a named or anonymous subroutine, and returns a hash reference whose keys are the possible numbers of returning scalars, and the corresponding values the "probability" to get them. A few special keys are also used :
 
-    { 1 => 0.2, 2 => 0.4, 4 => 0.3, list => 0.1 }
+=over 4
+
+=item *
+
+C<'list'> is used to denote a possibly infinite number of returned arguments ;
+
+=item *
+
+C<'exit'> gives the probability for C<exit> to be called somewhere in the code.
+
+=back
+
+The return value hence would look at
+
+    { 1 => 0.2, 2 => 0.4, 4 => 0.25, list => 0.1, exit => 0.05 }
 
 that is, we should get C<1> scalar C<1> time over C<5> and so on. The sum of all values is C<1>. The returned result, and all the results obtained from intermediate subs, are cached into the object.
 
@@ -105,9 +119,9 @@ never returns C<1> argument but returns C<2> with probability C<1/2 * 1/2 = 1/4>
 
 For example, C<stat> returns C<13> elements on success and C<0> on error. The according probability will then be C<< { 0 => 0.5, 13 => 0.5 } >>.
 
-=item * The C<list> state is absorbing in regard of all the other ones.
+=item * The C<list> and C<exit> states are absorbing in regard of all the other ones.
 
-This is just a pedantic way to say that "list + fixed length = list".
+This is just a pedantic way to say that C<list + fixed length = list>, C<exit + fixed length = exit>, but note also that C<exit + list = exit>.
 That's why
 
     sub listy {
@@ -116,7 +130,7 @@ That's why
 
 is considered as always returning an unbounded list.
 
-Also, the convolution law does not behave the same when C<list> elements are involved : in the following example,
+Also, the convolution law does not behave the same when C<list> or C<exit> elements are involved : in the following example,
 
     sub oneorlist {
      if (rand < 0.1) {
@@ -389,6 +403,21 @@ sub pp_anoncode {
  return $self->{sub} ? $self->enter($self->const_sv($op)) : (undef, 1)
 }
 
+sub pp_exit {
+ my ($self, $op) = @_;
+
+ my $r;
+ if ($op->flags & OPf_KIDS) {
+  ($r, my $l) = $self->inspect($op->first);
+  return $r, $l if defined $r and zero $l;
+  $r->{exit} = 1 - count $r;
+ } else {
+  $r = { 'exit' => 1 };
+ }
+
+ return $r, undef;
+}
+
 sub pp_goto {
  my ($self, $op) = @_;