diff --git a/lib/m2/ntoab.c b/lib/m2/ntoab.c
new file mode 100644
index 00000000..f2d2e3ad
--- /dev/null
+++ b/lib/m2/ntoab.c
@@ -0,0 +1,69 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2016,2017,2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes 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 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes 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 GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <mes/lib.h>
+#include <assert.h>
+#include <string.h>
+
+char *__itoa_buf;
+
+char *
+ntoab (long x, int base, int signed_p)
+{
+  if (__itoa_buf == 0)
+    __itoa_buf = malloc (20);
+
+  char *buf = __itoa_buf;
+  char *p = buf + 11;
+  p[0] = 0;
+  p = p - 1;
+  assert_msg (base > 0, "base  > 0");
+
+  int sign_p = 0;
+  unsigned u;
+  if (signed_p != 0 && x < 0)
+    {
+      sign_p = 1;
+      u = -x;
+    }
+  else
+    u = x;
+
+  do
+    {
+      unsigned i;
+      i = u % base;
+      u = u / base;
+      if (i > 9)
+        p[0] = 'a' + i - 10;
+      else
+        p[0] = '0' + i;
+      p = p - 1;
+    }
+  while (u != 0);
+
+  if (sign_p && p[1] != '0')
+    {
+      p[0] = '-';
+      p = p - 1;
+    }
+
+  return p + 1;
+}