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

/*************/
/* Arbres    */
/*************/

typedef enum {Var, Num, Op} Nature;

typedef union {
  char name;
  int val;
  struct op {
      char name;
      struct tcell *gauche,*droite;
    } op;
} Contenu;

typedef struct tcell {
  Nature nature;
  Contenu contenu;
} *Tree;

/* constructeurs des arbres */

Tree new_var(char name)
{
  ...
}

Tree new_num(int val)
{
  ...
}

Tree new_op(char name,Tree gauche,Tree droite)
{
  ...
}

void print_tree(Tree t)
{
  ...
}

/************************/
/*     Piles            */
/************************/

typedef struct lcell {
  Tree val;
  struct lcell *next;
} Cell, *Stack;

Stack stack = NULL;

Cell *cons(Tree val,Cell *next)
{
  Cell *r;

  r = (Cell *)malloc(sizeof(Cell));
  if ( r == NULL) {
    fprintf(stderr,"Plus de memoire\n");
    exit(-1);
  }
  r->val = val;
  r->next = next;
  return r;
}

void afficher(void)
{
  Stack p;

  printf("[");
  for (p=stack ; p != NULL ; p = p->next) {
    print_tree(p->val);
    if (p->next != NULL)
      printf(", ");
  }
  printf("]");
}

Tree pop(void)
{
  Tree r;

  if (stack == NULL) {
    fprintf(stderr,"Tentative de depiler une pile vide, adieu\n");
    exit(-1);
  }
  r = stack->val;
  stack = stack->next;
  return r;
}

void push(Tree i)
{
  stack = cons(i,stack);
}


Tree derive(Tree t, char var)
{

}

void main(void)
{
  char pgm[] = "xx*xdxd";
  char c;
  int i;
  Tree r1,r2;

  printf("    ");
  afficher();
  printf("\n");
  for(i=0; pgm[i] != '\0'; i++) {
    c = pgm[i];
    switch (c) {
    case '+':
    case '-':
    case '*':
    case '/':
      /* cas des operateurs */
      ....
    case 'd':
      /* cas de la derivation */
      ....
    default:
      /* cas des variables et des nombres */
    }
    printf("%c : ",c);
    afficher();
    printf("\n");
  }
}