Really basic tree walking library written in bash

treewalker.sh

# This program is free software. It comes without any warranty, to
# the extent permitted by applicable law. You can redistribute it
# and/or modify it under the terms of the Do What The Fuck You Want
# To Public License, Version 2, as published by Sam Hocevar. See
# http://sam.zoy.org/wtfpl/COPYING for more details.

# Private API

# treewalker.__walk head preCallback postCallback
treewalker.__walk() {
  local head="$1"
  if ! treewalker.in "$head" "${excludeList[@]}"; then
    excludeList+=("$head")
    local preCallback="$2"
    local postCallback="$3"
    [ -z "$preCallback" ] || $head.$preCallback
    local child
    for child in ${TREEWALKER_TREE[$head]}; do
      treewalker.__walk "$child" "$preCallback" "$postCallback"
    done
    [ -z "$postCallback" ] || $head.$postCallback
  fi
}

# treewalker.__reversedwalk head preCallback postCallback
treewalker.__reversedwalk() {
  local head="$1"
  if ! treewalker.in "$head" "${excludeList[@]}"; then
    excludeList+=("$head")
    local preCallback="$2"
    local postCallback="$3"
    [ -z "$preCallback" ] || $head.$preCallback
    local child
    for child in ${reversedTree[$head]}; do
      treewalker.__reversedwalk "$child" "$preCallback" "$postCallback"
    done
    [ -z "$postCallback" ] || $head.$postCallback
  fi
}

# Public API

# treewalker.in value [items...]
treewalker.in() {
  local val="$1"
  local item
  shift
  for item in "$@"; do
    [[ x"$val" = x"$item" ]] && return 0
  done
  return 1
}

# treewalker.walk head preCallback postCallback
treewalker.walk() {
  local -a excludeList=()
  treewalker.__walk "$1" "$2" "$3"
}

# treewalker.reversedwalk head preCallback postCallback
treewalker.reversedwalk() {
  local -A reversedTree
  local k
  local v
  local child
  for k in "${!TREEWALKER_TREE[@]}"; do
    for v in ${TREEWALKER_TREE[$k]}; do
      reversedTree[$v]+=" $k"
    done
  done

  local -a excludeList=()
  treewalker.__reversedwalk "$1" "$2" "$3"
}