[doc] Update README.md to match changes in DIY

README.md

@@ -11,7 +11,7 @@ possible in- and out-of-core in DIY.
 
 ## Licensing
 
-DIY is released as open source software under a BSD style [license](./LICENSE.txt).
+DIY is released as open source software under a BSD-style [license](./LICENSE.txt).
 
 ## Dependencies
 
@@ -26,7 +26,7 @@ DIY requires an MPI installation. We recommend [MPICH](http://www.mpich.org/).
 
 DIY is a header-only library. It does not need to be built; you can simply
 include it in your project. The examples can be built using `cmake` from the
-top level directory.
+top-level directory.
 
 ## Documentation
 
@@ -39,10 +39,10 @@ A simple DIY program, shown below, consists of the following components:
 - `struct`s called blocks,
 - a diy object called the `master`,
 - a set of callback functions performed on each block by `master.foreach()`,
-- optionally one or more message exchanges between the blocks by `master.exchange()`, and
+- optionally, one or more message exchanges between the blocks by `master.exchange()`, and
 - there may be other collectives and global reductions not shown below.
 
-The callback functions (`enqueue_block()` and `average()` in the example below) are given the block
+The callback functions (`enqueue_local()` and `average()` in the example below) receive the block
 pointer and a communication proxy for the message exchange between blocks. It is usual for the
 callback functions to enqueue or dequeue messages from the proxy, so that information can be
 received and sent during rounds of message exchange.
@@ -54,31 +54,24 @@ received and sent during rounds of message exchange.
 
     Master master(world);                               // world = MPI_Comm
     ...                                                 // populate master with blocks
-    master.foreach<Block>(&enqueue_local);              // call enqueue_local() for each block
+    master.foreach(&enqueue_local);                     // call enqueue_local() for each block
     master.exchange();                                  // exchange enqueued data between blocks
-    master.foreach<Block>(&average);                    // call average() for each block
+    master.foreach(&average);                           // call average() for each block
 
     // --- callback functions --- //
 
     // enqueue block data prior to exchanging it
-    void enqueue_local(Block* b,                        // one block
-                       const Proxy& cp,                 // communication proxy
-                                                        // i.e., the neighbor blocks with which
-                                                        // this block communicates
-                       void* aux)                       // user-defined additional arguments
+    void enqueue_local(Block* b,                        // current block
+                       const Proxy& cp)                 // communication proxy provides access to the neighbor blocks
     {
         for (size_t i = 0; i < cp.link()->size(); i++)  // for all neighbor blocks
-            cp.enqueue(cp.link()->target(i), b->local); // enqueue the data to be sent
-                                                        // to this neighbor block in the next
-                                                        // exchange
+            cp.enqueue(cp.link()->target(i), b->local); // enqueue the data to be sent to this neighbor
+                                                        // block in the next exchange
     }
 
     // use the received data after exchanging it, in this case compute its average
-    void average(Block* b,                              // one block
-                 const Proxy& cp,                       // communication proxy
-                                                        // i.e., the neighbor blocks with which
-                                                        // this block communicates
-                 void* aux)                             // user-defined additional arguments
+    void average(Block* b,                              // current block
+                 const Proxy& cp)                       // communication proxy provides access to the neighbor blocks
     {
         float x, average = 0;
         for (size_t i = 0; i < cp.link()->size(); i++)  // for all neighbor blocks