equivalent of bash command "ls -lt | head -n X" (you have to source it)

lt.sh

# This bash function is usefull to list most recent things in a directory.
#
# this script should not be run directly,
# instead you need to source it from your .bashrc,
# by adding this line:
#   . ~/bin/lt
#

lt() {
    comm="ls"
    opt="-lt"
    if [ -n "$LT_SHOW_HIDDEN" ];then
        if [ $LT_SHOW_HIDDEN -eq 1 ];then
            opt=$opt"a"
        fi
    fi
    if [ -n "$LT_REVERSE" ];then
        if [ $LT_REVERSE -eq 1 ];then
            opt=$opt"r"
        fi
    fi
    num=10
    usage="usage: lt [number] [directory_A] [directory_B]\nExample: 'lt 15 /var/log'\nDefault value for number is 10 (see head command)\nIf you do not want to see hidden files, set environment variable 'LT_SHOW_HIDDEN' to 1 before sourcing the lt.sh function.\nYou can also set LT_REVERSE to 1 to get the older files first."
    re='^[0-9]+$'
    if [ "$1" = "-h" ] || [ "$1" = "--help" ];then
        echo $usage
    elif [ -z "$1" ];then
        echo "$comm $opt |head -$((num+1))"
        $comm $opt |head -$((num+1))
    elif echo $1 |grep -Eq $re; then
        num=$1
        if [ -z "$2" ];then
            $comm $opt |head -$((num+1))
        else
            for dir in $@
            do
                shift
                if [ $dir != $num ]; then
                    echo $dir
                    $comm $opt $dir |head -$((num+1))
                fi
            done
        fi
    elif [ -d $1 ]; then
        # ok, user did not read the usage
        echo $usage
        if [ -z "$2" ];then
            $comm $opt $1 |head -$((num+1))
        elif echo $2 |grep -Eq $re;then
            num=$2
            $comm $opt $1 |head -$((num+1))
        else
            echo "The second arg is not a number. I will consider that other args are folders."
            for dir in $@
            do
                echo $dir
                $comm $opt $dir |head
            done
        fi
    else
        if [ -f $1 ]; then
            $comm $opt $1
        else
            echo $usage;
            echo "Are you sure that your argument is valid (existing and browsable directory/file) ?"
        fi;
    fi;
}

compatibility with zsh for LT_SHOW_HIDDEN and LT_REVERSE