std: remove substr & str::count_*, methodise char_len, implement slice_chars.

The confusing mixture of byte index and character count meant that every
use of .substr was incorrect; replaced by slice_chars which only uses
character indices. The old behaviour of `.substr(start, n)` can be emulated
via `.slice_from(start).slice_chars(0, n)`.

1 files changed, 1 insertions, 1 deletions

diff --git a/doc/tutorial.md b/doc/tutorial.md
index f487398d19c..a4580361166 100644
--- a/doc/tutorial.md
+++ b/doc/tutorial.md
@@ -1410,7 +1410,7 @@ let new_favorite_crayon_name = favorite_crayon_name.trim();
 
 if favorite_crayon_name.len() > 5 {
    // Create a substring
-   println(favorite_crayon_name.substr(0, 5));
+   println(favorite_crayon_name.slice_chars(0, 5));
 }
 ~~~