add pic_debug function

src/value.c

@@ -1,5 +1,16 @@
 #include "picrin.h"
 
+enum pic_tt
+pic_type(pic_value v)
+{
+  switch (v->type) {
+  case PIC_VTYPE_NIL:
+    return PIC_TT_NIL;
+  case PIC_VTYPE_HEAP:
+    return v->u->data->tt;
+  }
+}
+
 pic_value
 pic_nil_value()
 {

src/write.c

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "picrin.h"
+
+void
+pic_debug(pic_state *pic, pic_value obj)
+{
+  switch (pic_type(obj)) {
+  case PIC_TT_NIL:
+    printf("()");
+    break;
+  case PIC_TT_PAIR:
+    printf("(");
+    pic_debug(pic, pic_car(pic, obj));
+    printf(" . ");
+    pic_debug(pic, pic_cdr(pic, obj));
+    printf(")");
+    break;
+  case PIC_TT_SYMBOL:
+    printf("%s", pic_symbol_ptr(obj)->name);
+    break;
+  default:
+    abort();
+  }
+}