#!/bin/ksh

# Semordnilap

# # Variables:
#
integer MIN_WORD_LEN=1 TRUE=1 FALSE=0
dict='/home/ostrande/prj/roscode/unixdict.txt'

integer i j=0 k=0
typeset -A word

# # Functions:
#

# # Function _flipit(string) - return flipped string
#
function _flipit {
  typeset _buf ; _buf="$1"
  typeset _tmp ; unset _tmp

  for (( _i=$(( ${#_buf}-1 )); _i>=0; _i-- )); do
    _tmp="${_tmp}${_buf:${_i}:1}"
  done

  echo "${_tmp}"
}

# # Function _isword(word, wordlist) - return 1 if word in wordlist
#
function _isword {
  typeset _word ; _word="$1"
  typeset _wordlist ; nameref _wordlist="$2"

  [[ ${_word} == @(${_wordlist}) ]] && return $TRUE
  return $FALSE
}

 ######
# main #
 ######
# # Due to the large number of words in unixdist.txt subgroup by 1st letter and length
# # only accept words containing alpha chars and > 1 chars
#
while read; do
  [[ $REPLY != *+(\W)* ]] && [[ $REPLY != *+(\d)* ]] && \
    (( ${#REPLY} > MIN_WORD_LEN )) && word[${REPLY:0:1}][${#REPLY}]+=( $REPLY )
done < ${dict}

print Examples:
for fl in ${!word[*]}; do       # Over $fl first letter
  for len in ${!word[${fl}][*]}; do # Over $len word length
    for ((i=0; i<${#word[${fl}][${len}][*]}; i++)); do
      Word=${word[${fl}][${len}][i]}    # dummy
      Try=$(_flipit ${Word})
      if [[ ${Try} != ${Word} ]]; then  # no palindromes
        unset words
        oldIFS="$IFS" ; IFS='|' ; words=${word[${Try:0:1}][${#Try}][*]} ; IFS="${oldIFS}"
        _isword "${Try}" words
        if (( $? )); then
          if [[ ${Try} != @(${uniq%\|*}) ]]; then
            ((++j))
            (( ${#Word} >= 5 )) && (( k<=5 )) && print $((++k)). ${Word} ${Try}
            uniq+="${Try}|${Word}|"
          fi
        fi
      fi
    done
  done
done
echo ; print ${j} pairs found.