//This stream module demands alternating characters from the two sides.
#include <stdlib.h>
#include "pushy.h"
typedef struct {dnode dn; unode* un;} altS;
static void interleave(char c, dnode * n, unode* p){
  altS* pa = (altS*)n;
  unode* swp = pa->un;
  pa->un = p;
  (n->nsn->code)(c, n->nsn, swp);}

dnode* cinterleave(dnode* dn, unode* un){
  altS* an = (altS*)malloc(sizeof(altS));
  *an = (altS){(dnode){interleave, dn}, un};
  return &an->dn;}