Added docs

docs/api/srfi/111.md

@@ -1,21 +1,24 @@
 # SRFI 111 - Boxes
 
-The `(srfi 111)` library ...
+The `(srfi 111)` library defines boxes, a container for an object of any Scheme type, including another box. Boxes are normally used as minimal mutable storage, and can inject a controlled amount of mutability into an otherwise immutable data structure (or one that is conventionally treated as immutable). 
 
 See the [SRFI document](http://srfi.schemers.org/srfi-111/srfi-111.html) for more information.
 
-##- [`and-let*`](#and-let)
+- [`box`]     (#box)
-##
+- [`box?`]    (#box-1) 
-###and-let*
+- [`unbox`]   (#unbox) 
-##    (and-let* (claws) body
+- [`set-box!`](#set-box)
-##
+
-##    claws ::= '() | (cons claw claws)
+#box 
-##    claw  ::=  (variable expression) | (expression) |
+    (box value)
-##               bound-variable
+Constructor. Returns a newly allocated box initialized to value.
-##
+#box?
-##- The `claws` are evaluated in the strict left-to-right order
+    (box? object)
-##- For each `claw`, the `expression` part is evaluated first (or `bound-variable` is looked up)
+Predicate. Returns #t if object is a box, and #f otherwise.
-##- If the result is #f, `and-let*` immediately returns #f
+#unbox
-##- Otherwise, if the `claw` is of the form `(variable expression)` the `expression`'s value is bound to a freshly made `variable`
+    (unbox box)
-##- The `variable` is available for the rest of the `claws` , and the `body`
+Accessor. Returns the current value of box.
-##- As usual, all `variable`s must be unique (like in `let*`)
+#set-box!
+    (set-box! box value)
+Mutator. Changes box to hold value.
+