text: #ifndef EVAL_STACK_H
  # define EVAL_STACK_H
  
  # include <unistd.h>
  # include "ops.h"
  
  typedef struct opstack
  {
      const s_op **ops;
      size_t size;
      size_t size_max;
  } s_opstack;
  
  s_opstack *opstack_init(void);
  void opstack_push(s_opstack *s, const s_op *op);
  const s_op *opstack_pop(s_opstack *s);
  void opstack_free(s_opstack *s);
  
  typedef struct numstack
  {
      long *nums;
      size_t size;
      size_t size_max;
  } s_numstack;
  
  s_numstack *numstack_init(void);
  void numstack_push(s_numstack *s, long num);
  int numstack_pop(s_numstack *s);
  void numstack_free(s_numstack *s);
  
  #endif /* !EVAL_STACK_H */
  