--*- coding: utf-8; -*--


			       INF2270
		 L?sningsforslag oppgaver uke 6 2013

Oppgave 1

#define STREQ(s1,s2) (strcmp((s1),(s2))==0)


Oppgave 2

Det finnes mange l?sninger, blant annet

    x = MIN(a,b) + 1;
    x = 1 - MIN(a,4);

Disse vil bli ekspandert til henholdsvis

    x = a<b ? a : b+1;
    x = 1-a<4 ? a : 4;

(Jeg har justert litt med blanke tegn for ? gj?re det tydeligere
hvorledes C-kompilatoren vil oppfatte uttrykket.)


Oppgave 3

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

int main(int argc, char *argv[])
{
  FILE *f;
  int nc = 0, nw = 0, nl = 0, /* Antall tegn, ord, linjer */
      c, 
      in_word = 0;

  if (argc != 2) {
    printf("Usage: wc file\n");  return 1;
  }
  f = fopen(argv[1],"r");
  if (f == NULL) {
    printf("wc: %s: No such file or directory\n", argv[1]);
    return 2;
  }

  c = fgetc(f);
  while (c != EOF) {
    nc++;
    if (c == '\n') nl++;
    if (isspace(c)) {
      in_word = 0;
    } else {
      if (! in_word) nw++;
      in_word = 1;
    }
    c = fgetc(f);
  }
  fclose(f);

  printf("%8d%8d%8d %s\n", nl, nw, nc, argv[1]);
  return 0;
}


Oppgave 4

#include <stdio.h>
#include <stdlib.h>
#include <string.h>


struct line_struct {
  struct line_struct *next;
  char contents[203];  /* 200 characters + CR and/or LF + 0-byte */
};
typedef struct line_struct line;


line *read_all_lines (FILE *f)
{
  line *first = NULL;
  char cur_line[203];
  
  while (fgets(cur_line,202,f) != NULL) {
    line *cur = malloc(sizeof(line));
    strcpy(cur->contents, cur_line);

    /* Insert this line first in the list: */
    cur->next = first;
    first = cur;
  }
  return first;
}


void print_all_lines (line *lp)
{
  while (lp) {
    printf("%s", lp->contents);
    lp = lp->next;
  }
}


void remove_all_lines (line *lp)
{
  if (lp == NULL) return;
  remove_all_lines(lp->next);
  free(lp);
}


int main (int argc, char *argv[])
{
  if (argc != 2) {
    printf("Usage: tac filename\n");
    exit(1);
  }

  FILE *f = fopen(argv[1],"r");
  if (f == NULL) {
    printf("tac: Cannot read %s!\n", argv[1]);
    exit(2);
  }

  line *data = read_all_lines(f);
  print_all_lines(data);
  remove_all_lines(data);  data = NULL;
  return 0;
}