+ My_lily_parser *parser = unsmob_my_lily_parser (parser_smob);
+ Book *book = unsmob_book (book_smob);
+ Output_def *bp = unsmob_output_def (parser->lexer_->lookup_identifier ("$defaultbookpaper"));
+
+ SCM_ASSERT_TYPE (parser, parser_smob, SCM_ARG1, __FUNCTION__, "Lilypond parser");
+ SCM_ASSERT_TYPE (book, book_smob, SCM_ARG2, __FUNCTION__, "Book");
+
+ /* ugh. changing argument.*/
+ book->bookpaper_ = bp;
+
+ File_name outname (parser->output_basename_);
+ int *c = &parser->book_count_;
+ if (*c)
+ outname.base_ += "-" + to_string (*c);
+ (*c)++;
+
+ Output_def *paper = get_paper (parser);
+
+ Paper_book* pb = book->process (outname.to_string (), paper);
+
+ pb->output (outname.to_string ());
+
+ scm_gc_unprotect_object (paper->self_scm ());
+ scm_gc_unprotect_object (pb->self_scm ());
+
+ return SCM_UNSPECIFIED;