1 files changed, 24 insertions, 1 deletions

diff --git a/doc/styleguide.txt b/doc/styleguide.txt
index 31ad4469..2251e773 100644
--- a/doc/styleguide.txt
+++ b/doc/styleguide.txt
@@ -61,7 +61,7 @@ need that kind of processing (e.g. file and command names). The
 _filedir and _filedir_xspec helpers do this automatically whenever
 they return some completions.
 
-[[ $COMPREPLY == *= ]] && compopt -o nospace
+[[ ${COMPREPLY-} == *= ]] && compopt -o nospace
 ------------------------------------------------
 
 The above is functionally a shorthand for:
@@ -95,6 +95,29 @@ explicitly handled (non-completed) in the $prev handling block because
 --foo=bar options can often be written without the equals sign, and in
 that case the long option splitting does not occur.
 
+Use arithmetic evaluation
+-------------------------
+
+When dealing with numeric data, take advantage of arithmetic evaluation.
+In essence, use (( ... )) whenever it can replace [[ ... ]] because the
+syntax is more readable; no need for $-prefixes, numeric comparison etc
+operators are more familiar and easier on the eye.
+
+Array subscript access
+----------------------
+
+Array subscripts are arithmetic expressions, take advantage of that.
+E.g. write ${foo[bar]}, not ${foo[$bar]}, and similarly ${foo[bar+1]}
+vs ${foo[((bar+1))]} or ${foo[$((bar+1))]}, ${foo[--i]} vs ${foo[((--i))]}.
+
+Loop variable names
+-------------------
+
+Use i, j, k for loop-local indices; n and m for lengths; some other descriptive
+name typically based on array name but in singular when looping over actual
+values. If an index or value is to be accessed later on instead of being just
+locally for looping, use a more descriptive and specific name for it.
+
 /////////////////////////////////////////
 case/esac vs if
 ---------------