1 files changed, 121 insertions, 0 deletions
diff --git a/tools/bison++/derives.cc b/tools/bison++/derives.cc
new file mode 100644
index 000000000..17b9ec5ff
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+++ b/tools/bison++/derives.cc
@@ -0,0 +1,121 @@
+/* Match rules with nonterminals for bison,
+   Copyright (C) 1984, 1989 Free Software Foundation, Inc.
+
+This file is part of Bison, the GNU Compiler Compiler.
+
+Bison is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+Bison is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with Bison; see the file COPYING.  If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+
+/* set_derives finds, for each variable (nonterminal), which rules can derive it.
+   It sets up the value of derives so that
+   derives[i - ntokens] points to a vector of rule numbers,
+   terminated with -1.  */
+
+#include <stdio.h>
+#include "system.h"
+#include "new.h"
+#include "types.h"
+#include "gram.h"
+
+#ifdef	DEBUG
+static void print_derives(void);
+#endif
+
+short **derives;
+
+void
+set_derives()
+{
+  register int i;
+  register int lhs;
+  register shorts *p;
+  register short *q;
+  register shorts **dset;
+  register shorts *delts;
+
+  dset = NEW2(nvars, shorts *) - ntokens;
+  delts = NEW2(nrules + 1, shorts);
+
+  p = delts;
+  for (i = nrules; i > 0; i--)
+    {
+      lhs = rlhs[i];
+      if (lhs >= 0)
+	{
+	  p->next = dset[lhs];
+	  p->value = i;
+	  dset[lhs] = p;
+	  p++;
+	}
+    }
+
+  derives = NEW2(nvars, short *) - ntokens;
+  q = NEW2(nvars + nrules, short);
+
+  for (i = ntokens; i < nsyms; i++)
+    {
+      derives[i] = q;
+      p = dset[i];
+      while (p)
+	{
+	  *q++ = p->value;
+	  p = p->next;
+	}
+      *q++ = -1;
+    }
+
+#ifdef	DEBUG
+  print_derives();
+#endif
+
+  FREE(dset + ntokens);
+  FREE(delts);
+}
+
+void
+free_derives()
+{
+  FREE(derives[ntokens]);
+  FREE(derives + ntokens);
+}
+
+
+
+#ifdef	DEBUG
+
+void print_derives(void)
+{
+  register int i;
+  register short *sp;
+
+  extern char **tags;
+
+  printf("\n\n\nDERIVES\n\n");
+
+  for (i = ntokens; i < nsyms; i++)
+    {
+      printf("%s derives", tags[i]);
+      for (sp = derives[i]; *sp > 0; sp++)
+	{
+	  printf("  %d", *sp);
+	}
+      putchar('\n');
+    }
+
+  putchar('\n');
+}
+
+#endif
+