inarray() and isarray() functions for bash (to check whether value exist)

inarray.bash

# look for a value in an array, returns 0 on success, 1 otherwise
# Usage: in_array "$needle" "${haystack[@]}"

inarray()
{   
    [ -z "$1" ] && return 1

    if [ -n "$BASH" ]; then
        _inarray_var_needle="$1"
        shift
        for element
        do
            [ X"$element" != X"$_inarray_var_needle" ] || return 0
        done
    fi
    return 1
}