DP=3
MOD=1000

function ftofix {       # ftofix OUTPUTNAME "3.14"
        local _N="0"
        local D=0
        local X
        local Y

        # Convert "VAR" "-.3" into "VAR" "-" "0.3", etc
        case "$2" in
        [.]*)           set -- "$1" "" "0$2"            ;;
        [0-9]*)         set -- "$1" "" "$2"             ;;
        [+-][0-9.]*)    set -- "$1" "${2:0:1}" "${2:1}" ;;
        *)              return 1                        ;;
        esac

        for((X=0; X<${#3}; X++))
        do
                if [[ "${3:$X:1}" == "." ]]
                then
                        (( X++ )) ; break
                fi

                (( _N = (10*_N) + ${3:$X:1} ))
        done

        while [[ "$D" -lt "$DP" ]]
        do
                Y="${3:$((X+D)):1}"
                [ -z "$Y" ] && Y=0

                (( _N = (10*_N) + Y ))
                (( D++ ))
        done

        read "$1" <<EOF
${2}${_N}
EOF
}

function fixtof {
        _VAR="$1"
        _N="$2"
        _SIGN=""
        ((_N<0)) && _SIGN="-" && ((_N=-_N))
        _S=`printf "%s%d.%0${DP}d" "${_SIGN}" $((_N/MOD)) $((_N%MOD))`
        read $_VAR <<EOF
$_S
EOF
}

AA="3.14159"
BB="-0.073"

ftofix B $BB
ftofix A $AA

# Multiplcation
fixtof CC $(((A*B)/MOD))
echo "$AA * $BB = $CC"

# Division
fixtof DD $(( (A*MOD)/B ))
echo "$AA / $BB = $DD"

# Addition and Subtraction
fixtof EE $(( B - A ))
echo "$BB - $AA = $EE"
fixtof FF $(( A - B ))
echo "$AA - $BB = $FF"
fixtof GG $(( A + B ))
echo "$AA + $BB = $GG"

3.14159 * -0.073 = -0.229
3.14159 / -0.073 = -43.027
-0.073 - 3.14159 = -3.214
3.14159 - -0.073 = 3.214
3.14159 + -0.073 = 3.068