toolset: parser and unparser

Intended usage from the shell command line

$ echo '(1+1) * (1+1)' | parser | unparser
or even:
$ echo '(1+1) * (1+1)' | parser | unparser | parser | unparser

Parser main routine:

#include "y.tab.h"   /* yacc (token) definitions */
#include "k.h"                 /* data type defs */
#include "csgiok.h"    /* structure file io defs */

expr the_expr;         /* root of the parse tree */

int main() {
  char *io;            /* error message, or == 0 */
  yyparse();                    /* invoke parser */
  io = CSGIOwrite_expr(stdout, the_expr);
  if (io != 0)                         /* error! */
      fatal("Write error: %s\n", io);
  exit(0);                           /* success! */
}

#include "k.h"                 /* data type defs */
#include "csgiok.h"    /* structure file io defs */
#include "unpk.h"         /* unparse (view) defs */
#include "printer.h"     /* printer function def */

int main() {
  char *io;            /* error message, or == 0 */
  expr the_expr;       /* root of the parse tree */
  io = CSGIOread_expr(stdin, &the_expr);
  if (io != 0)                         /* error! */
      fatal("Read error: %s\n", io);
  unparse_expr(the_expr, printer, base_view);
  exit(0);                           /* success! */
}