Meanwhile you may use functions to setup your variables something along
those lines.
PW$ function first-index { echo $1; }
PW$ function last-index { shift $(($#-1)) ; echo $1; }
PW$ declare -a array=([5]="hello" [11]="world" [42]="here")
PW$ declare -i first_index=$(first-index ${!array[@]})
PW$
Currently, to know the index of an array's indexes (example: first or
last index), it needs an intermediary index array:
#!/usr/bin/env bash
declare -a array=([5]=hello [11]=world [42]=here)
declare -ai indexes=("${!array[@]}")
declare -i first_index=${indexes[*]:0:1}
declare -i last_index=${i
