#include <stdlib.h>
#include "pushy.h"
// A splitter links a unode together with a dnode by embedding the
// unode in a dupS, which locates the unode by field "mate".
typedef struct {dnode n; dnode * bSt; char s; unode* mate,* sav;} dupS;
static void dupa(char c, dupS * n, unode* p){
  n->s = c;
  n->sav = p;
  {dnode* dn = (dnode*)n;
  (dn->nsn->code)(c, dn->nsn, n->mate);}}
static void dupb(unode* p){dupS* ds = (dupS*)(p->dn);
  (ds->bSt->code)(ds->s, ds->bSt, ds->sav);}
dnode* ctee(dnode* s1, dnode* s2){
  dupS* dn = malloc(sizeof(dupS));
  unode* un = malloc(sizeof(unode));
  *dn = (dupS){(dnode){(push)dupa, s1}, s2, 0, un, 0};
  *un = (unode){dupb, &(dn->n)};
  return &(dn->n);}