round - shortens integer down to a desired length & rounds it up, down or to nearest value

##############################################################################################
# round v1.9 - shortens integer down to a desired length & rounds it up, down or to nearest  #
#  value using floating point arithmetic or parameter expansion.                             #
# Handshake:                                                                                 #
# $1 contains the value to be processed. Must be integer and >0.                             #
# $2 contains the desired length in digits. Must be integer, >0 and < or = the length of $1. #
# False & missing inputs give a return code 1 which can be requested for error handling.     #
# Result will be printed to stdout.                                                          #
##############################################################################################

RND_PREP(){ # checks if input is valid & prepares divisor for rounding
    [ $((${1##*[!0-9]*}+0)) -eq 0 ] || [ $((${2##*[!0-9]*}+0)) -eq 0 ] && return 1 || RND_RES=$1
    [ ${#1} -lt $2 ] && return 1
    RND_DIV=$(printf 1'%*s' $((${#1}-$2)) | tr " " 0)
}

RND_NEAR1(){ # cuts down to desired length & rounds to nearest value using parameter expansion
    RND_PREP $1 $2 || return 1
    printf "%.0f" "${RND_RES}e-$((${#RND_DIV}-1))"
}

RND_NEAR2(){ # similar to NEAR1, but a little more accurate using floating point arithmetic
    RND_PREP $1 $2 || return 1
    printf $((($RND_RES+$RND_DIV/2)/$RND_DIV))
}

RND_NEAR3(){ # like NEAR2, but even more precise rounding as if it's shortened recursively
    RND_PREP $1 $2 || return 1
    printf $((($RND_RES+$RND_DIV*10/18)/$RND_DIV))
}

RND_FLOOR(){ # divides down to desired length & rounds always down
    RND_PREP $1 $2 || return 1
    printf $(($1/$RND_DIV))
}

RND_CEIL(){ # divides down to desired length & rounds always up
    RND_PREP $1 $2 || return 1
    printf $((($1+$RND_DIV-1)/$RND_DIV))
}