add object printer

main.c

@@ -9,6 +9,7 @@ int main(void) {
   addroot(&p);
 
   collect();
+  println(p);
 
   gcfinalize();
   return 0;

print.c

@@ -1,3 +1,62 @@
+#include "inttypes.h"
 #include "wscm.h"
+#include <stdio.h>
 
-// TODO.
+void print(O obj);
+
+void printcons(O obj) {
+  O c = obj;
+  I f = 1;
+
+  printf("(");
+  while (c != NIL && !IMM(c)) {
+    H *h = UNBOX(c);
+    if (h->type != OBJ_CONS) {
+      printf(" . ");
+      print(c);
+      printf(")");
+      return;
+    }
+    C *p = (C *)(h + 1);
+    if (!f)
+      printf(" ");
+    f = 0;
+    print(p->head);
+    c = p->tail;
+  }
+  if (c != NIL && !IMM(c)) {
+    printf(" . ");
+    print(c);
+  }
+  printf(")");
+}
+
+void print(O obj) {
+  if (obj == NIL) {
+    printf("()");
+  } else if (IMM(obj)) {
+    printf("%" PRIdPTR, ORD(obj));
+  } else {
+    void *x = (void *)UNBOX(obj);
+    if (((const U8 *)x) >= heap.from.start && ((const U8 *)x) < heap.from.end) {
+      H *h = (H *)x;
+      switch (h->type) {
+      case OBJ_CONS:
+        printcons(obj);
+        break;
+      default:
+        printf("<obj type=%" PRIdPTR " @ %p>", h->type, (void *)h);
+        break;
+      }
+    } else {
+      // If pointer is outside the heap, it's a symbol.
+      S *s = (S *)x;
+      printf("%.*s", (int)s->len, s->data);
+    }
+  }
+}
+
+void println(O obj) {
+  print(obj);
+  putchar('\n');
+}

wscm.h

@@ -83,3 +83,6 @@ O mksym(const char *str);
 
 O cons(O head, O tail);
 C *uncons(O obj);
+
+void print(O obj);
+void println(O obj);