diff --git a/modules/environment/init.zsh b/modules/environment/init.zsh
index 142170b..6216310 100644
--- a/modules/environment/init.zsh
+++ b/modules/environment/init.zsh
@@ -39,7 +39,7 @@ unsetopt HUP
 unsetopt CHECK_JOBS
 
 # Set less or more as the default pager.
-if (( ${+PAGER} )); then
+if ! (( ${+PAGER} )); then
   if (( ${+commands[less]} )); then
     export PAGER=less
   else
diff --git a/modules/fasd/functions/fasd b/modules/fasd/functions/fasd
index b19a6f8..3646949 100644
--- a/modules/fasd/functions/fasd
+++ b/modules/fasd/functions/fasd
@@ -41,20 +41,20 @@ case $1 in
         fi
 
         # set default options
-        (( "${+_FASD_DATA}" )) && _FASD_DATA="$HOME/.fasd"
-        (( "${+_FASD_BLACKLIST}" )) && _FASD_BLACKLIST="--help"
-        (( "${+_FASD_SHIFT}" )) && _FASD_SHIFT="sudo busybox"
-        (( "${+_FASD_IGNORE}" )) && _FASD_IGNORE="fasd ls echo"
-        (( "${+_FASD_SINK}" )) && _FASD_SINK=/dev/null
-        (( "${+_FASD_TRACK_PWD}" )) && _FASD_TRACK_PWD=1
-        (( "${+_FASD_MAX}" )) && _FASD_MAX=2000
-        (( "${+_FASD_BACKENDS}" )) && _FASD_BACKENDS=native
-        (( "${+_FASD_FUZZY}" )) && _FASD_FUZZY=2
-        (( "${+_FASD_VIMINFO}" )) && _FASD_VIMINFO="$HOME/.viminfo"
-        (( "${+_FASD_RECENTLY_USED_XBEL}" )) && \
+        ! (( "${+_FASD_DATA}" )) && _FASD_DATA="$HOME/.fasd"
+        ! (( "${+_FASD_BLACKLIST}" )) && _FASD_BLACKLIST="--help"
+        ! (( "${+_FASD_SHIFT}" )) && _FASD_SHIFT="sudo busybox"
+        ! (( "${+_FASD_IGNORE}" )) && _FASD_IGNORE="fasd ls echo"
+        ! (( "${+_FASD_SINK}" )) && _FASD_SINK=/dev/null
+        ! (( "${+_FASD_TRACK_PWD}" )) && _FASD_TRACK_PWD=1
+        ! (( "${+_FASD_MAX}" )) && _FASD_MAX=2000
+        ! (( "${+_FASD_BACKENDS}" )) && _FASD_BACKENDS=native
+        ! (( "${+_FASD_FUZZY}" )) && _FASD_FUZZY=2
+        ! (( "${+_FASD_VIMINFO}" )) && _FASD_VIMINFO="$HOME/.viminfo"
+        ! (( "${+_FASD_RECENTLY_USED_XBEL}" )) && \
           _FASD_RECENTLY_USED_XBEL="$HOME/.local/share/recently-used.xbel"
 
-        if (( "${+_FASD_AWK}" )); then
+        if ! (( "${+_FASD_AWK}" )); then
           # awk preferences
           local awk; for awk in mawk gawk original-awk nawk awk; do
             $awk "" && _FASD_AWK=$awk && break
@@ -125,7 +125,7 @@ case $1 in
   # add current pwd if the option is set
   [ "$_FASD_TRACK_PWD" = "1" -a "$PWD" != "$HOME" ] && paths="$paths|$PWD"
 
-  (( "${+paths##\|}" )) && return # stop if we have nothing to add
+  ! (( "${+paths##\|}" )) && return # stop if we have nothing to add
 
   # maintain the file
   local tempfile
@@ -312,12 +312,12 @@ $(fasd --backend $each)"
   while [ "$1" ]; do case $1 in
     --complete) [ "$2" = "--" ] && shift; set -- $2; local lst=1 r=r comp=1;;
     --query|--add|--delete|-A|-D) fasd "$@"; return $?;;
-    --version) (( "${+comp}" )) && echo "1.0.1" && return;;
+    --version) ! (( "${+comp}" )) && echo "1.0.1" && return;;
     --) while [ "$2" ]; do shift; fnd="$fnd $1"; last="$1"; done;;
     -*) local o="${1#-}"; while [ "$o" ]; do case $o in
         s*) local show=1;;
         l*) local lst=1;;
-        i*) (( "${+comp}" )) && local interactive=1 show=1;;
+        i*) ! (( "${+comp}" )) && local interactive=1 show=1;;
         r*) local mode=rank;;
         t*) local mode=recent;;
         e*) o="${o#?}"; if [ "$o" ]; then # there are characters after "-e"
@@ -343,7 +343,7 @@ $(fasd --backend $each)"
         f*) local typ=f;;
         R*) local r=r;;
     [0-9]*) local _fasd_i="$o"; break;;
-        h*) (( "${+comp}" )) && echo "fasd [options] [query ...]
+        h*) ! (( "${+comp}" )) && echo "fasd [options] [query ...]
 [f|a|s|d|z] [options] [query ...]
   options:
     -s         list paths with scores
@@ -376,7 +376,7 @@ fasd [-A|-D] [paths ...]
          fi;;
   esac
 
-  local R; (( "${+r}" )) && R=r || R= # let $R be the opposite of $r
+  local R; ! (( "${+r}" )) && R=r || R= # let $R be the opposite of $r
   fnd="${fnd# }"
 
   local res
@@ -407,7 +407,7 @@ fasd [-A|-D] [paths ...]
   fi
   if [ "$res" ]; then
     fasd --add "$res"
-    (( "${+exec}" )) && exec='printf %s\n'
+    ! (( "${+exec}" )) && exec='printf %s\n'
     $exec "$res"
   fi
   ;;
diff --git a/modules/fasd/init.zsh b/modules/fasd/init.zsh
index 8fdffa4..c14720e 100644
--- a/modules/fasd/init.zsh
+++ b/modules/fasd/init.zsh
@@ -6,7 +6,7 @@ fasd_cd() {
     fasd "$@"
   else
     local _fasd_ret="$(fasd -e 'printf %s' "$@")"
-    (( "${+_fasd_ret}" )) && return
+    ! (( "${+_fasd_ret}" )) && return
     [ -d "$_fasd_ret" ] && cd "$_fasd_ret" || printf %s\n "$_fasd_ret"
   fi
 }
@@ -44,7 +44,7 @@ compctl -U -K _fasd_zsh_cmd_complete -V fasd -x 'C[-1,-*e],s[-]n[1,e]' -c - \
   # zsh word mode completion
   _fasd_zsh_word_complete() {
     [ "$2" ] && local _fasd_cur="$2"
-    (( "${+_fasd_cur}" )) && local _fasd_cur="${words[CURRENT]}"
+    ! (( "${+_fasd_cur}" )) && local _fasd_cur="${words[CURRENT]}"
     local fnd="${_fasd_cur//,/ }"
     local typ=${1:-e}
     fasd --query $typ "$fnd" 2>> "/dev/null" | \
diff --git a/modules/git/functions/git-submodule-move b/modules/git/functions/git-submodule-move
index 8eadc1d..df1fa45 100644
--- a/modules/git/functions/git-submodule-move
+++ b/modules/git/functions/git-submodule-move
@@ -12,7 +12,7 @@ local url
 
 url="$(command git config --file "$(git-root)/.gitmodules" --get "submodule.${src}.url")"
 
-if (( "${+url}" )); then
+if ! (( "${+url}" )); then
   print "${0}: submodule not found: ${src}" >&2
   return 1
 fi