diff --git a/tokenize.l b/tokenize.l
index 26bab15..b47c405 100644
--- a/tokenize.l
+++ b/tokenize.l
@@ -26,6 +26,7 @@ struct ast {
   } v;
   struct ast *next;
 };
+ 
 
 enum asttype {
   AST_TOK  = 400,
@@ -88,101 +89,155 @@ make_token(enum yytokentype type, int num, char* str)
 }
 
 struct ast*
-make_ast(enum asttype type, struct token *t, struct ast *n) {
+make_ast(enum asttype type, struct token *t)
+{
   struct ast *a = (struct ast*) calloc(1, sizeof(struct ast));
   if (a == NULL)
     err(1, "malloc failed");
   a->type = type;
   if (type == AST_TOK)
     a->v.token = t;
-  else if (type == AST_LIST)
-    a->v.list = n; 
+  /* else if (type == AST_LIST) */
+  /*   a->v.list = n;  */
   return a;
 }
 
+struct token *next;
 struct ast*
 parse(struct token *t)
 {
   if (t == NULL)
     err(1, "Unexpected token: <NULL>");
-  if (t->type == LPAR) {
-    struct ast *head;
-    struct ast *a = head = make_ast(AST_LIST, NULL, NULL);
+
+ if (t->type == LPAR) {
+    struct ast *head = make_ast(AST_LIST, NULL);
+    struct ast *a, *p;
     t = t->next;
-    assert (t != NULL);
     while (t->type != RPAR) {
-      a->next = parse(t);
-      t = t->next;
+      assert (t != NULL);
+      a = parse(t);
+      if (a == NULL)
+        err(1, "syntax error");
+      if (head->v.list == NULL)  {
+        p = head->v.list = a;
+      } else {
+        p->next = a;
+      }
+      p = a;
+      t = next;        /* skip all tokens that are processed */
+      assert(t != NULL);
     }
+      fprintf(stderr, "a=%p, t=%p\n", a, t);
     assert(t->type == RPAR);
     t = t->next;
+    next = t;
     return head;
   } else if (t->type == NUM) {
     printf("is a number %d\n", t->v.num);
-    return make_ast(AST_TOK, t, NULL);
+    next = t->next;
+    return make_ast(AST_TOK, t);
   } else if (t->type == SYM) {
-    printf("is a sym: %s\n", t->v.str);
-    return make_ast(AST_TOK, t, NULL);
+   printf("is a sym: %s (%p)\n", t->v.str, t);
+    next = t->next;
+    return make_ast(AST_TOK, t);
   } else if (t->type == STR) {
+    next = t->next;
     printf("is a str: %s\n", t->v.str);
-    return make_ast(AST_TOK, t, NULL);
+    return make_ast(AST_TOK, t);
   }
   return NULL;
 }
 
+
+
 void
-debug_token(struct token *x) {
-  fprintf(stderr, "%d: ", x->type);
-  if (x->type == NUM) fprintf(stderr, "%d", x->v.num);
+debug_token(struct token *x, indent) {
+  for (int i = 0; i < indent; i++) putc(' ', stderr);
+  fprintf(stderr, "%d: (%p)", x->type, x);
+  if (x->type == NUM) fprintf(stderr, "%d @ %p", x->v.num, x);
   if (x->type == STR || x->type == SYM)
     fprintf(stderr, "%s", x->v.str);
   putc('\n', stderr);
 }
 
 void
-debug_ast(struct ast *a) {
+debug_ast(struct ast *a, indent) {
   while (a) {
-    fprintf(stderr, "AST: %s", (a->type == AST_TOK) ? "AST_TOK" :
-            "AST_LIST");
-    fprintf(stderr, " [%p]", (a->type == AST_TOK) ? a->v.list :
-            a->v.token);
+    for (int i = 0; i < indent; i++) putc(' ', stderr);
+    fprintf(stderr, "AST: %s,a=%p,list=%p,token=%p,next=%p", (a->type == AST_TOK) ? "AST_TOK" :
+            "AST_LIST", a, a->v.list, a->v.token, a->next);
     putc('\n', stderr);
-    if (a->type == AST_LIST) debug_ast(a->v.list);
+    if (a->type == AST_LIST) {
+      fprintf(stderr, "enter %p\n", a->v.list);
+      fprintf(stderr, "==\n");
+      debug_ast(a->v.list, indent+4);
+      fprintf(stderr, "==\n");
+    }
     else if(a->type == AST_TOK)
-      debug_token(a->v.token);
+      debug_token(a->v.token, indent);
     a = a->next;
   }
 }
 
+struct ast *
+eval(struct ast *a)
+{
+  if (a->type == AST_TOK) {
+    if (a->v.token->type == NUM) {
+      return make_ast(AST_TOK, a->v.token);
+    }
+    else if (a->v.token->type == SYM) {
+      if (strcmp(a->v.token->v.str, "def") == 0) {
+        printf("define: %s\n", a->next->v.token->v.str);
+        /* x = eval a->next->next */
+        /* install:  var:=x */
+      }
+
+    } else if (a->v.token->type == STR)
+      fprintf(stderr, "str\n");
+  } else if (a->type == AST_LIST) {
+    eval(a->v.list);
+  } else {
+    fprintf(stderr, "%d\n", a->type);
+    assert(0);
+  }
+  return NULL;
+}
+
+void
+pr(struct ast *a)
+{
+  switch (a->type) {
+  case AST_TOK:
+    if (a->v.token->type == NUM)
+      printf("%d\n", a->v.token->v.num);
+  }
+}
+
 int main(void)
 {
   int tok;
   struct token *t, *u = NULL, *start = NULL;
 
   while(tok = yylex()) {
-    //printf("token: %d, %d, %s\n", tok, yylval, yytext);
-    //printf("t=%p\n", t);
-    //if(t->type == NUMBER) printf(" = %d\n", t->v.num);
-
-    /* form=read_form() .. */
-    /* eval(form) */
-
+    /* read token and create list */
     t = make_token(tok, yylval, yytext);
     if (start == NULL) start = t;
     if (u == NULL)     u = t;
     else               u->next = t;
     u = t;
     
+    /* if EOL is reached, parse and evaluate form: */
     if (t->type == EOL) {
       struct token *x = start;
-      while (x != NULL) {
-        debug_token(x);
-        x = x->next;
-      }
+      // while (x != NULL) {debug_token(x, 0); x = x->next;}
      
-      struct ast *tl = parse(start);
-      debug_ast(tl);
-      /* XXX: eval(parse(start)) */
+      /* struct ast *tl = parse(start); */
+      /* eval(tl); */
+      eval(parse(start));
+      //debug_ast(tl, 1);
+      
+      /* start anew: */
       start = NULL;
     }
   }