/* File: list-io.c
 * Author: Jim Mayfield
 */

#include <stdio.h>
#include <ctype.h>

typedef int list_item_type;
#include "lists.h"
#include "list-io.h"

static
void
print_int_list_items(FILE *outfile, list_type list)
{
  printf("%d", first(list));
  if (!empty_list(rest(list))) {
    putc(' ', outfile);
    print_int_list_items(outfile, rest(list));
  }
}

void
print_int_list(FILE *outfile, list_type list)
{
  putc('<', outfile);
  if (!empty_list(list))
    print_int_list_items(outfile, list);
  putc('>', outfile);
}

static
list_type
read_int_list_items(FILE *infile)
{
  int item;

  if (fscanf(infile, "%d", &item) == 1)
    return(cons(item, read_int_list_items(infile)));
  else return(the_empty_list);
}

list_type
read_int_list(FILE *infile)
{
  int c;
  list_type result;

  while ((c = getc(infile)) != EOF && isspace(c));
  if (c == EOF) {
    fprintf(stderr, "ERROR: end-of-file encountered in read_int_list.\n");
    return(the_empty_list);
  }
  if (c != '<') {
    ungetc(c, infile);
    fprintf(stderr, "ERROR: read_int_list expects lists to begin with '<'.\n"
	            "   (A '%c' was found instead).\n",
	    c);
    return(the_empty_list);
  }
  result = read_int_list_items(infile);
  while ((c = getc(infile)) != EOF && isspace(c));
  if (c == EOF) {
    fprintf(stderr, "ERROR: end-of-file encountered in read_int_list.\n");
    return(result);
  }
  if (c != '>') {
    ungetc(c, infile);
    fprintf(stderr, "ERROR: read_int_list expects lists to end with '>'.\n"
	            "   (A '%c' was found instead).\n",
	    c);
    return(result);
  }
  return(result);
}