Merge branch 'master' of github.com:hadley/r4ds

functions.Rmd

@@ -146,7 +146,7 @@ Compared to the original, this code is easier to understand and we've eliminated
     ```
 
 1.  Read the [complete lyrics](https://en.wikipedia.org/wiki/Little_Bunny_Foo_Foo) 
-    to "Little Bunny Foo". There's a lot of duplication in this song. 
+    to "Little Bunny Foo Foo". There's a lot of duplication in this song. 
     Extend the initial piping example to recreate the complete song, and use 
     functions to reduce the duplication.
 
@@ -279,6 +279,14 @@ if (NA) {}
 
 You can use `||` (or) and `&&` (and) to combine multiple logical expressions. These operators are "short-circuiting": as soon as `||` sees the first `TRUE` it returns `TRUE` without computing anything else. As soon as `&&` sees the first `FALSE` it returns `FALSE`. You should never use `|` or `&` in an `if` statement: these are vectorised operations that apply to multiple values. If you do have a logical vector, you can use `any()` or `all()` to collapse it to a single value.
 
+You can enforce this more-strictly by using the `identical()` function, which returns either a single `TRUE` or a single `FALSE`. One thing to watch out for is that *you* have to be more strict when specifying integers:
+
+```{r}
+if (i == 0){}
+
+if (identical(i, 0L)){}
+```
+
 ### Multiple conditions
 
 You can chain multiple if statements together: