td1.cc

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#include<iostream>

// Exercice 1
// a)

int& hop(int& x) {
  return x;
}

//b)
int& hip(int t[], int i) {
  return t[i];
}

// Exercice 2
void byte_print(long l) {
  // 2.d)
  struct conf{
    conf(){ std::cout << std::hex;}
    ~conf(){ std::cout << std::dec;}
  } cn;
  // fin 2.d)
  unsigned char* c = (unsigned char*) &l;
  for(int i=0; i<sizeof(long); ++i){
    if(i>0)
      std::cout << '.';
    std::cout << (unsigned) *(c+i);
  }
  std::cout << std::endl;
}

//b
void byte_swap(void* p, void* q) {
  unsigned char & c = *((unsigned char*) p);
  unsigned char & d = *((unsigned char*) q);
  c^=d; d^=c; c^=d;
}

//c
void big_to_little(long& l) {
  unsigned char* p=(unsigned char*)&l;
  for(int i=0; i<sizeof(long)/2; ++i)
    byte_swap(p+i, p+(sizeof(long)-1)-i);
}

// Exercice 3
unsigned f(unsigned n, unsigned x, unsigned y) {
  if(n==0) return x;
  for(unsigned i=1u; i<n; ++i) {
    y=x+y;
    x=y-x;
  }
  return y;
} 

unsigned f(unsigned n, unsigned x=0u) {
  return f(n,1,x);
}

int main() {
  // exo 1
  int x;
  hop(x)=4;
  std::cout << x << std::endl; // affiche 4
  int t[6];
  hip(t,3)=5;
  std::cout << t[3] << std::endl; // affiche 5
  // exo 2
  long l=246346L;
  byte_print(l);
  big_to_little(l);
  byte_print(l);
  return 0;
}