[PATCH 7/8] CodingGuidelines: on comparison
See http://thread.gmane.org/gmane.comp.version-control.git/3903/focus=4126
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
Documentation/CodingGuidelines | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
index 21e4272..86fb9f6 100644
--- a/Documentation/CodingGuidelines
+++ b/Documentation/CodingGuidelines
@@ -212,6 +212,32 @@ For C programs:
- Double negation is often harder to understand than no negation
at all.
+ - There are two schools of thought when it comes to comparison,
+ especially inside a loop. Some people prefer to have less stable
+ value on the left hand side and more stable value on the right hand
+ side, e.g. if you have a loop that counts variable i down to the
+ lower bound,
+
+ while (i > lower_bound) {
+ do something;
+ i--;
+ }
+
+ Other people prefer to have the textual order of values match the
+ actual order of values in their comparison, so that they can
+ mentally draw a number line from left to right and place these
+ values in order, i.e.
+
+ while (lower_bound < i) {
+ do something;
+ i--;
+ }
+
+ Both are valid, and we use both, even though we tend to see the
+ former the more preferable, the more "stable" the more stable side
+ becomes (comparison with a constant, "i > 0", is an extreme
+ example). Just do not mix styles in the same part of the code.
+
- Some clever tricks, like using the !! operator with arithmetic
constructs, can be extremely confusing to others. Avoid them,
unless there is a compelling reason to use them.
--
2.0.0-rc1-355-gd6d6511
Junio C Hamano <gitster@pobox.com>