Document unwind_var.

1 files changed, 20 insertions, 3 deletions

diff --git a/crawl-ref/source/unwind.h b/crawl-ref/source/unwind.h
index 426d629225..c13dda320b 100644
--- a/crawl-ref/source/unwind.h
+++ b/crawl-ref/source/unwind.h
@@ -1,29 +1,46 @@
 #ifndef UNWIND_H
 #define UNWIND_H
 
+/** Type that gives an lvalue dynamically-scoped temporary value.  An
+ * unwind_var remembers the old value of a variable or other writable lvalue,
+ * and restores the original (or a specified) value when the unwind_var goes
+ * out of scope or is otherwise destroyed.
+ */
 template <typename T>
 class unwind_var
 {
 public:
-    unwind_var(T &val_, T newval, T reset_to) : val(val_), oldval(reset_to)
+    /** Wrap the lvalue val_ and on unwinding restore its original value. */
+    unwind_var(T &val_) : val(val_), oldval(val_) { }
+
+    /** Wrap the lvalue val_, assign it the temporary value newval, and
+     *  on unwinding restore its original value.
+     */
+    unwind_var(T &val_, T newval) : val(val_), oldval(val_)
     {
         val = newval;
     }
-    unwind_var(T &val_, T newval) : val(val_), oldval(val_)
+
+    /** Wrap the lvalue val_, assign it the temporary value newval, and
+     *  on unwinding assign it the value reset_to.
+     */
+    unwind_var(T &val_, T newval, T reset_to) : val(val_), oldval(reset_to)
     {
         val = newval;
     }
-    unwind_var(T &val_) : val(val_), oldval(val_) { }
+
     ~unwind_var()
     {
         val = oldval;
     }
 
+    /** Get the current (temporary) value of the wrapped lvalue. */
     T value() const
     {
         return val;
     }
 
+    /** Get the value that will be used to restore the wrapped lvalue. */
     T original_value() const
     {
         return oldval;