Merge pull request #135 from jirutka/redrawhook

Fix compatibility with latest zsh-syntax-highlighting (zle-line-pre-redraw) and use memo= feature

.gitignore

@@ -1,2 +1,2 @@
-# zsh word code files (zcompile)
-*.zwc
+# zsh word code files (zcompile and zrecompile)
+*.zwc*

README.md

@@ -17,6 +17,27 @@ Requirements
 
 * [ZSH](http://zsh.sourceforge.net) 4.3 or newer
 
+Install
+------------------------------------------------------------------------------
+
+Using the [Homebrew]( https://brew.sh ) package manager:
+
+    brew install zsh-history-substring-search
+    echo 'source /usr/local/share/zsh-history-substring-search/zsh-history-substring-search.zsh' >> ~/.zshrc
+
+Using [Oh-my-zsh](https://github.com/robbyrussell/oh-my-zsh):
+
+1. Clone this repository in oh-my-zsh's plugins directory:
+
+        git clone https://github.com/zsh-users/zsh-history-substring-search ${ZSH_CUSTOM:-~/.oh-my-zsh/custom}/plugins/zsh-history-substring-search
+
+2. Activate the plugin in `~/.zshrc`:
+
+        plugins=( [plugins...] zsh-history-substring-search)
+
+3. Source `~/.zshrc`  to take changes into account:
+
+        source ~/.zshrc
 
 Usage
 ------------------------------------------------------------------------------
@@ -35,24 +56,32 @@ Usage
 
     Users typically bind their UP and DOWN arrow keys to this script, thus:
     * Run `cat -v` in your favorite terminal emulator to observe key codes.
+      (**NOTE:** In some cases, `cat -v` shows the wrong key codes.  If the
+      key codes shown by `cat -v` don't work for you, press `<C-v><UP>` and
+      `<C-v><DOWN>` at your ZSH command line prompt for correct key codes.)
     * Press the UP arrow key and observe what is printed in your terminal.
     * Press the DOWN arrow key and observe what is printed in your terminal.
     * Press the Control and C keys simultaneously to terminate the `cat -v`.
     * Use your observations from the previous steps to create key bindings.
       For example, if you observed `^[[A` for UP and `^[[B` for DOWN, then:
 
-            bindkey '^[[A' history-substring-search-up
-            bindkey '^[[B' history-substring-search-down
+          bindkey '^[[A' history-substring-search-up
+          bindkey '^[[B' history-substring-search-down
 
-    You might also want to bind the Control-P/N keys for use in EMACS mode:
+      However, if the observed values don't work, you can try using terminfo:
 
-        bindkey -M emacs '^P' history-substring-search-up
-        bindkey -M emacs '^N' history-substring-search-down
+          bindkey "$terminfo[kcuu1]" history-substring-search-up
+          bindkey "$terminfo[kcud1]" history-substring-search-down
 
-    You might also want to bind the `k` and `j` keys for use in VI mode:
+      You might also want to bind the Control-P/N keys for use in EMACS mode:
 
-        bindkey -M vicmd 'k' history-substring-search-up
-        bindkey -M vicmd 'j' history-substring-search-down
+          bindkey -M emacs '^P' history-substring-search-up
+          bindkey -M emacs '^N' history-substring-search-down
+
+      You might also want to bind the `k` and `j` keys for use in VI mode:
+
+          bindkey -M vicmd 'k' history-substring-search-up
+          bindkey -M vicmd 'j' history-substring-search-down
 
 3.  Type any part of any previous command and then:
 
@@ -86,7 +115,7 @@ Configuration
 ------------------------------------------------------------------------------
 
 This script defines the following global variables. You may override their
-default values only after having loaded this script into your ZSH session.
+default values.
 
 * `HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND` is a global variable that defines
   how the query should be highlighted inside a matching command. Its default
@@ -107,6 +136,17 @@ default values only after having loaded this script into your ZSH session.
   Flags" section in the zshexpn(1) man page to learn about the kinds of
   values you may assign to this variable.
 
+* `HISTORY_SUBSTRING_SEARCH_FUZZY` is a global variable that defines
+  how the command history will be searched for your query. If set to a non-empty
+  value, causes this script to perform a fuzzy search by words, matching in
+  given order e.g. `ab c` will match `*ab*c*`
+
+* `HISTORY_SUBSTRING_SEARCH_PREFIXED` is a global variable that defines how
+  the command history will be searched for your query. If set to a non-empty
+  value, your query will be matched against the start of each history entry.
+  For example, if this variable is empty, `ls` will match `ls -l` and `echo
+  ls`; if it is non-empty, `ls` will only match `ls -l`.
+
 * `HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE` is a global variable that defines
   whether all search results returned are _unique_. If set to a non-empty
   value, then only unique search results are presented. This behaviour is off

zsh-history-substring-search.plugin.zsh

@@ -0,0 +1,2 @@
+0=${(%):-%N}
+source ${0:A:h}/zsh-history-substring-search.zsh

zsh-history-substring-search.zsh

@@ -7,6 +7,7 @@
 # Copyright (c) 2011 Sorin Ionescu
 # Copyright (c) 2011 Vincent Guerci
 # Copyright (c) 2016 Geza Lore
+# Copyright (c) 2017 Bengt Brodersen
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -39,34 +40,32 @@
 ##############################################################################
 
 #-----------------------------------------------------------------------------
-# declare global variables
+# declare global configuration variables
+#-----------------------------------------------------------------------------
+
+: ${HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND='bg=magenta,fg=white,bold'}
+: ${HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND='bg=red,fg=white,bold'}
+: ${HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS='i'}
+: ${HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE=''}
+: ${HISTORY_SUBSTRING_SEARCH_FUZZY=''}
+: ${HISTORY_SUBSTRING_SEARCH_PREFIXED=''}
+
+#-----------------------------------------------------------------------------
+# declare internal global variables
 #-----------------------------------------------------------------------------
 
 typeset -g BUFFER MATCH MBEGIN MEND CURSOR
-typeset -g HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
-typeset -g HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND
-typeset -g HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS
-typeset -g HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE
 typeset -g _history_substring_search_refresh_display
 typeset -g _history_substring_search_query_highlight
 typeset -g _history_substring_search_result
 typeset -g _history_substring_search_query
-typeset -g -A _history_substring_search_raw_matches
-typeset -g _history_substring_search_raw_match_index
-typeset -g -A _history_substring_search_matches
+typeset -g -a _history_substring_search_query_parts
+typeset -g -a _history_substring_search_raw_matches
+typeset -g -i _history_substring_search_raw_match_index
+typeset -g -a _history_substring_search_matches
+typeset -g -i _history_substring_search_match_index
 typeset -g -A _history_substring_search_unique_filter
-typeset -g _history_substring_search_match_index
-
-#-----------------------------------------------------------------------------
-# configuration variables
-#-----------------------------------------------------------------------------
-
-typeset -g HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND='bg=magenta,fg=white,bold'
-typeset -g HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND='bg=red,fg=white,bold'
-typeset -g HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS='i'
-typeset -g HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE=''
-typeset -g _history_substring_search_{refresh_display,query_highlight,result,query,match_index,raw_match_index}
-typeset -ga _history_substring_search{,_raw}_matches
+typeset -g -i _history_substring_search_zsh_5_9
 
 #-----------------------------------------------------------------------------
 # the main ZLE widgets
@@ -100,6 +99,11 @@ zle -N history-substring-search-down
 #-----------------------------------------------------------------------------
 
 zmodload -F zsh/parameter
+autoload -Uz is-at-least
+
+if is-at-least 5.9 $ZSH_VERSION; then
+  _history_substring_search_zsh_5_9=1
+fi
 
 #
 # We have to "override" some keys and widgets if the
@@ -120,80 +124,125 @@ if [[ $+functions[_zsh_highlight] -eq 0 ]]; then
   }
 
   #
-  # The following snippet was taken from the zsh-syntax-highlighting project:
+  # Check if $1 denotes the name of a callable function, i.e. it is fully
+  # defined or it is marked for autoloading and autoloading it at the first
+  # call to it will succeed. In particular, if $1 has been marked for
+  # autoloading but is not available in $fpath, then it will return 1 (false).
   #
-  # https://github.com/zsh-users/zsh-syntax-highlighting/blob/56b134f5d62ae3d4e66c7f52bd0cc2595f9b305b/zsh-syntax-highlighting.zsh#L126-161
+  # This is based on the zsh-syntax-highlighting plugin.
   #
-  # Copyright (c) 2010-2011 zsh-syntax-highlighting contributors
-  # All rights reserved.
+  _history-substring-search-function-callable() {
+    if (( ${+functions[$1]} )) && ! [[ "$functions[$1]" == *"builtin autoload -X"* ]]; then
+      return 0 # already fully loaded
+    else
+      # "$1" is either an autoload stub, or not a function at all.
+      # We expect 'autoload +X' to return non-zero if it fails to fully load
+      # the function.
+      ( autoload -U +X -- "$1" 2>/dev/null )
+      return $?
+    fi
+  }
+
   #
-  # Redistribution and use in source and binary forms, with or without
-  # modification, are permitted provided that the following conditions are
-  # met:
+  # The zsh-syntax-highlighting plugin uses zle-line-pre-redraw hook instead
+  # of the legacy "bind all widgets" if 1) zsh has the memo= feature (added in
+  # version 5.9) and 2) add-zle-hook-widget is available.
   #
-  #  * Redistributions of source code must retain the above copyright
-  #    notice, this list of conditions and the following disclaimer.
-  #
-  #  * Redistributions in binary form must reproduce the above copyright
-  #    notice, this list of conditions and the following disclaimer in the
-  #    documentation and/or other materials provided with the distribution.
-  #
-  #  * Neither the name of the zsh-syntax-highlighting contributors nor the
-  #    names of its contributors may be used to endorse or promote products
-  #    derived from this software without specific prior written permission.
-  #
-  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
-  # IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
-  # THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
-  # PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
-  # CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
-  # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
-  # PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
-  # PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
-  # LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
-  # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
-  # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-  #
-  #--------------8<-------------------8<-------------------8<-----------------
-  # Rebind all ZLE widgets to make them invoke _zsh_highlights.
-  _zsh_highlight_bind_widgets()
-  {
-    # Load ZSH module zsh/zleparameter, needed to override user defined widgets.
-    zmodload zsh/zleparameter 2>/dev/null || {
-      echo 'zsh-syntax-highlighting: failed loading zsh/zleparameter.' >&2
-      return 1
+  if [[ $_history_substring_search_zsh_5_9 -eq 1 ]] && _history-substring-search-function-callable add-zle-hook-widget; then
+    #
+    # The following code is based on the zsh-syntax-highlighting plugin.
+    #
+    autoload -U add-zle-hook-widget
+
+    _history-substring-search-zle-line-finish() {
+      #
+      # Reset $WIDGET since the 'main' highlighter depends on it.
+      #
+      # Since $WIDGET is declared by zle as read-only in this function's scope,
+      # a nested function is required in order to shadow its built-in value;
+      # see "User-defined widgets" in zshall.
+      #
+      () {
+        local -h -r WIDGET=zle-line-finish
+        _zsh_highlight
+      }
     }
 
-    # Override ZLE widgets to make them invoke _zsh_highlight.
-    local cur_widget
-    for cur_widget in ${${(f)"$(builtin zle -la)"}:#(.*|_*|orig-*|run-help|which-command|beep|yank*)}; do
-      case $widgets[$cur_widget] in
+    _history-substring-search-zle-line-pre-redraw() {
+      #
+      # If the zsh-syntax-highlighting plugin has been loaded (after our plugin
+      # plugin, otherwise this hook wouldn't be called), remove our hooks.
+      #
+      if [[ $+ZSH_HIGHLIGHT_VERSION -eq 1 ]]; then
+        autoload -U add-zle-hook-widget
+        add-zle-hook-widget -d zle-line-pre-redraw _history-substring-search-zle-line-pre-redraw
+        add-zle-hook-widget -d zle-line-finish _history-substring-search-zle-line-finish
+        return 0
+      fi
+      #
+      # Set $? to 0 for _zsh_highlight.  Without this, subsequent
+      # zle-line-pre-redraw hooks won't run, since add-zle-hook-widget happens to
+      # call us with $? == 1 in the common case.
+      #
+      true && _zsh_highlight "$@"
+    }
 
-        # Already rebound event: do nothing.
-        user:$cur_widget|user:_zsh_highlight_widget_*);;
+    if [[ -o zle ]]; then
+      add-zle-hook-widget zle-line-pre-redraw _history-substring-search-zle-line-pre-redraw
+      add-zle-hook-widget zle-line-finish _history-substring-search-zle-line-finish
+    fi
+  else
+    #
+    # The following snippet was taken from the zsh-syntax-highlighting project:
+    # https://github.com/zsh-users/zsh-syntax-highlighting/blob/56b134f5d62ae3d4e66c7f52bd0cc2595f9b305b/zsh-syntax-highlighting.zsh#L126-161
+    #
+    # SPDX-SnippetBegin
+    # SPDX-License-Identifier: BSD-3-Clause
+    # SPDX-SnippetCopyrightText: 2010-2011 zsh-syntax-highlighting contributors
+    #--------------8<-------------------8<-------------------8<-----------------
+    # Rebind all ZLE widgets to make them invoke _zsh_highlights.
+    _zsh_highlight_bind_widgets()
+    {
+      # Load ZSH module zsh/zleparameter, needed to override user defined widgets.
+      zmodload zsh/zleparameter 2>/dev/null || {
+        echo 'zsh-syntax-highlighting: failed loading zsh/zleparameter.' >&2
+        return 1
+      }
 
-        # User defined widget: override and rebind old one with prefix "orig-".
-        user:*) eval "zle -N orig-$cur_widget ${widgets[$cur_widget]#*:}; \
-                      _zsh_highlight_widget_$cur_widget() { builtin zle orig-$cur_widget -- \"\$@\" && _zsh_highlight }; \
-                      zle -N $cur_widget _zsh_highlight_widget_$cur_widget";;
+      # Override ZLE widgets to make them invoke _zsh_highlight.
+      local cur_widget
+      for cur_widget in ${${(f)"$(builtin zle -la)"}:#(.*|_*|orig-*|run-help|which-command|beep|yank*)}; do
+        case $widgets[$cur_widget] in
 
-        # Completion widget: override and rebind old one with prefix "orig-".
-        completion:*) eval "zle -C orig-$cur_widget ${${widgets[$cur_widget]#*:}/:/ }; \
-                            _zsh_highlight_widget_$cur_widget() { builtin zle orig-$cur_widget -- \"\$@\" && _zsh_highlight }; \
-                            zle -N $cur_widget _zsh_highlight_widget_$cur_widget";;
+          # Already rebound event: do nothing.
+          user:$cur_widget|user:_zsh_highlight_widget_*);;
 
-        # Builtin widget: override and make it call the builtin ".widget".
-        builtin) eval "_zsh_highlight_widget_$cur_widget() { builtin zle .$cur_widget -- \"\$@\" && _zsh_highlight }; \
-                       zle -N $cur_widget _zsh_highlight_widget_$cur_widget";;
+          # User defined widget: override and rebind old one with prefix "orig-".
+          user:*) eval "zle -N orig-$cur_widget ${widgets[$cur_widget]#*:}; \
+                        _zsh_highlight_widget_$cur_widget() { builtin zle orig-$cur_widget -- \"\$@\" && _zsh_highlight }; \
+                        zle -N $cur_widget _zsh_highlight_widget_$cur_widget";;
 
-        # Default: unhandled case.
-        *) echo "zsh-syntax-highlighting: unhandled ZLE widget '$cur_widget'" >&2 ;;
-      esac
-    done
-  }
-  #-------------->8------------------->8------------------->8-----------------
+          # Completion widget: override and rebind old one with prefix "orig-".
+          completion:*) eval "zle -C orig-$cur_widget ${${widgets[$cur_widget]#*:}/:/ }; \
+                              _zsh_highlight_widget_$cur_widget() { builtin zle orig-$cur_widget -- \"\$@\" && _zsh_highlight }; \
+                              zle -N $cur_widget _zsh_highlight_widget_$cur_widget";;
 
-  _zsh_highlight_bind_widgets
+          # Builtin widget: override and make it call the builtin ".widget".
+          builtin) eval "_zsh_highlight_widget_$cur_widget() { builtin zle .$cur_widget -- \"\$@\" && _zsh_highlight }; \
+                         zle -N $cur_widget _zsh_highlight_widget_$cur_widget";;
+
+          # Default: unhandled case.
+          *) echo "zsh-syntax-highlighting: unhandled ZLE widget '$cur_widget'" >&2 ;;
+        esac
+      done
+    }
+    #-------------->8------------------->8------------------->8-----------------
+    # SPDX-SnippetEnd
+
+    _zsh_highlight_bind_widgets
+  fi
+
+  unfunction _history-substring-search-function-callable
 fi
 
 _history-substring-search-begin() {
@@ -223,6 +272,7 @@ _history-substring-search-begin() {
     # speed things up a little.
     #
     _history_substring_search_query=
+    _history_substring_search_query_parts=()
     _history_substring_search_raw_matches=()
 
   else
@@ -233,20 +283,38 @@ _history-substring-search-begin() {
     _history_substring_search_query=$BUFFER
 
     #
-    # $BUFFER contains the text that is in the command-line currently.
-    # we put an extra "\\" before meta characters such as "\(" and "\)",
-    # so that they become "\\\(" and "\\\)".
+    # compose search pattern
     #
-    local escaped_query=${BUFFER//(#m)[\][()|\\*?#<>~^]/\\$MATCH}
+    if [[ -n $HISTORY_SUBSTRING_SEARCH_FUZZY ]]; then
+      #
+      # `=` split string in arguments
+      #
+      _history_substring_search_query_parts=(${=_history_substring_search_query})
+    else
+      _history_substring_search_query_parts=(${==_history_substring_search_query})
+    fi
 
     #
-    # Find all occurrences of the search query in the history file.
+    # Escape and join query parts with wildcard character '*' as seperator
+    # `(j:CHAR:)` join array to string with CHAR as seperator
+    #
+    local search_pattern="${(j:*:)_history_substring_search_query_parts[@]//(#m)[\][()|\\*?#<>~^]/\\$MATCH}*"
+
+    #
+    # Support anchoring history search to the beginning of the command
+    #
+    if [[ -z $HISTORY_SUBSTRING_SEARCH_PREFIXED ]]; then
+      search_pattern="*${search_pattern}"
+    fi
+
+    #
+    # Find all occurrences of the search pattern in the history file.
     #
     # (k) returns the "keys" (history index numbers) instead of the values
     # (R) returns values in reverse older, so the index of the youngest
     # matching history entry is at the head of the list.
     #
-    _history_substring_search_raw_matches=(${(k)history[(R)(#$HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS)*${escaped_query}*]})
+    _history_substring_search_raw_matches=(${(k)history[(R)(#$HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS)${search_pattern}]})
   fi
 
   #
@@ -265,8 +333,7 @@ _history-substring-search-begin() {
   #
   _history_substring_search_raw_match_index=0
   _history_substring_search_matches=()
-  unset _history_substring_search_unique_filter
-  typeset -A -g _history_substring_search_unique_filter
+  _history_substring_search_unique_filter=()
 
   #
   # If $_history_substring_search_match_index is equal to
@@ -296,12 +363,21 @@ _history-substring-search-begin() {
 _history-substring-search-end() {
   setopt localoptions extendedglob
 
+  local highlight_memo=
   _history_substring_search_result=$BUFFER
 
+  if [[ $_history_substring_search_zsh_5_9 -eq 1 ]]; then
+    highlight_memo='memo=history-substring-search'
+  fi
+
   # the search was successful so display the result properly by clearing away
   # existing highlights and moving the cursor to the end of the result buffer
   if [[ $_history_substring_search_refresh_display -eq 1 ]]; then
-    region_highlight=()
+    if [[ -n $highlight_memo ]]; then
+      region_highlight=( "${(@)region_highlight:#*${highlight_memo}*}" )
+    else
+      region_highlight=()
+    fi
     CURSOR=${#BUFFER}
   fi
 
@@ -309,16 +385,23 @@ _history-substring-search-end() {
   _zsh_highlight
 
   # highlight the search query inside the command line
-  if [[ -n $_history_substring_search_query_highlight && -n $_history_substring_search_query ]]; then
-    #
-    # The following expression yields a variable $MBEGIN, which
-    # indicates the begin position + 1 of the first occurrence
-    # of _history_substring_search_query in $BUFFER.
-    #
-    : ${(S)BUFFER##(#m$HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS)($_history_substring_search_query##)}
-    local begin=$(( MBEGIN - 1 ))
-    local end=$(( begin + $#_history_substring_search_query ))
-    region_highlight+=("$begin $end $_history_substring_search_query_highlight")
+  if [[ -n $_history_substring_search_query_highlight ]]; then
+    # highlight first matching query parts
+    local highlight_start_index=0
+    local highlight_end_index=0
+    local query_part
+    for query_part in $_history_substring_search_query_parts; do
+      local escaped_query_part=${query_part//(#m)[\][()|\\*?#<>~^]/\\$MATCH}
+      # (i) get index of pattern
+      local query_part_match_index="${${BUFFER:$highlight_start_index}[(i)(#$HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS)${escaped_query_part}]}"
+      if [[ $query_part_match_index -le ${#BUFFER:$highlight_start_index} ]]; then
+        highlight_start_index=$(( $highlight_start_index + $query_part_match_index ))
+        highlight_end_index=$(( $highlight_start_index + ${#query_part} ))
+        region_highlight+=(
+          "$(($highlight_start_index - 1)) $(($highlight_end_index - 1)) ${_history_substring_search_query_highlight}${highlight_memo:+,$highlight_memo}"
+        )
+      fi
+    done
   fi
 
   # For debugging purposes:
@@ -447,7 +530,7 @@ _history_substring_search_process_raw_matches() {
     #
     # Move on to the next raw entry and get its history index.
     #
-    (( _history_substring_search_raw_match_index++ ))
+    _history_substring_search_raw_match_index+=1
     local index=${_history_substring_search_raw_matches[$_history_substring_search_raw_match_index]}
 
     #
@@ -627,7 +710,7 @@ _history-substring-search-up-search() {
     # 1. Move index to point to the next match.
     # 2. Update display to indicate search found.
     #
-    (( _history_substring_search_match_index++ ))
+    _history_substring_search_match_index+=1
     _history-substring-search-found
 
   else
@@ -638,7 +721,7 @@ _history-substring-search-up-search() {
     #    _history_substring_search_matches.
     # 2. Update display to indicate search not found.
     #
-    (( _history_substring_search_match_index++ ))
+    _history_substring_search_match_index+=1
     _history-substring-search-not-found
   fi
 
@@ -707,7 +790,7 @@ _history-substring-search-down-search() {
     # 1. Move index to point to the previous match.
     # 2. Update display to indicate search found.
     #
-    (( _history_substring_search_match_index-- ))
+    _history_substring_search_match_index+=-1
     _history-substring-search-found
 
   else
@@ -718,7 +801,7 @@ _history-substring-search-down-search() {
     #    _history_substring_search_matches.
     # 2. Update display to indicate search not found.
     #
-    (( _history_substring_search_match_index-- ))
+    _history_substring_search_match_index+=-1
     _history-substring-search-not-found
   fi