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perl/Examples/Chap4/make-genes-1

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+
+
+###
+### make_genes
+###
+
+## Chapter 4 section 3.2
+
+sub make_genes {
+  my $pat = shift;
+  my @tokens = split /[()]/, $pat;
+  for (my $i = 1; $i < @tokens; $i += 2) {
+    $tokens[$i] = [0, split(//, $tokens[$i])];
+  }
+  my $FINISHED = 0;
+  return Iterator {
+    return if $FINISHED;
+    my $finished_incrementing = 0;
+    my $result = "";
+    for my $token (@tokens) {
+      if (ref $token eq "") {    # plain string
+        $result .= $token;
+      } else {                   # wildcard
+        my ($n, @c) = @$token;
+        $result .= $c[$n];
+        unless ($finished_incrementing) {
+          if ($n == $#c) { $token->[0] = 0 }
+          else { $token->[0]++; $finished_incrementing = 1 }
+        }                
+      }
+    }
+    $FINISHED = 1 unless $finished_incrementing;
+    return $result;
+  }
+}