---

yaml
---
r: 15619
b: refs/heads/try
c: 55e29ef
h: refs/heads/master
i:
  15617: 13b3445
  15615: d916bbd
v: v3

Author: catamorphism

[refs]

@@ -2,5 +2,5 @@
 refs/heads/master: 61b1875c16de39c166b0f4d54bba19f9c6777d1a
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: 4a81779abd786ff22d71434c6d9a5917ea4cdfff
-refs/heads/try: 03d9d6287ba09bbfb7c0dfe8977e6629ea5066e1
+refs/heads/try: 55e29ef4aa88d5d16b2ac6880cf1ab39ae11de90
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105

branches/try/doc/tutorial.md

@@ -729,7 +729,8 @@ top-level module will be called `foo`, and you can set `RUST_LOG` to
 `foo` to enable `warn`, `info` and `debug` logging for the module.
 
 Turned-off `log` statements impose minimal overhead on the code that
-contains them, so except in code that needs to be really, really fast,
+contains them, because the arguments to `log` are evaluated lazily.
+So except in code that needs to be really, really fast,
 you should feel free to scatter around debug logging statements, and
 leave them in.
 
@@ -743,6 +744,9 @@ and will log the formatted string:
 #error("fatal: %s", get_error_string());
 ~~~~
 
+Because the macros `#debug`, `#warn`, and `#error` expand to calls to `log`,
+their arguments are also lazily evaluated.
+
 ## Assertions
 
 The keyword `assert`, followed by an expression with boolean type,