nestlog: expand ex2

README.md

@@ -49,7 +49,7 @@ output:
 - indentation reflects call structure. We don't see anything for `main()`,
   since we didn't put any logging there
 
-### 2
+### 2 slightly more elaborate
 
 ```
 /* examples ex2/ex2.cpp */
@@ -89,6 +89,9 @@ main(int argc, char ** argv) {
     log && log("<- :fib(n) ", fn);
 }
 ```
+- global configuration settings live in the `xo::log_config` class.  see [log_config.hpp](include/nestlog/log_config.hpp)
+- the recommended form `log && log(...)` tests whether logging at this site is enabled /before/ evaluating/formatting the log message;
+  when logging is disabled,  this saves the cost of computing and formatting that message.
 
 output:
 ![ex2 output](img/ex2.png)

example/ex1/ex1.cpp

@@ -2,13 +2,17 @@
 
 using namespace xo;
 
-void A(int x) {
-    XO_SCOPE(log, info);
+void inner(int x) {
+    scope log(XO_ENTER0(always), ":x ", x);
+}
 
-    log("x:", x);
+void outer(int y) {
+    scope log(XO_ENTER0(always), ":y ", y);
+
+    inner(2*y);
 }
 
 int
 main(int argc, char ** argv) {
-    A(66);
+    outer(123);
 }