Updated readme

README.md

@@ -31,23 +31,25 @@ That's it!
 ```julia
 using XDiag
 
-let 
-    N = 16;
-    nup = N ÷ 2;
-    block = Spinhalf(N, nup);
+let
+    say_hello()
+    N = 16
+    nup = N ÷ 2
+    block = Spinhalf(N, nup)
 
     # Define the nearest-neighbor Heisenberg model
     ops = OpSum()
     for i in 1:N
-        ops += Op("HB", "J", [i, mod1(i+1, N)])
+        ops += "J" * Op("SdotS", [i, mod1(i+1, N)])
     end
-    ops["J"] = 1.0;
+    ops["J"] = 1.0
 
-    set_verbosity(2);           # set verbosity for monitoring progress
-    e0 = eigval0(ops, block);   # compute ground state energy
+    set_verbosity(2)            # set verbosity for monitoring progress
+    e0 = eigval0(ops, block)    # compute ground state energy
 
-    println("Ground state energy: $e0");
+    println("Ground state energy: $e0")
 end
+
 ```
 
 ### Documentation