gistfile1.txt

irb(main):132:0> str
=> "a b 'c  d'  e"
irb(main):133:0> scan(str)
=> ["a", "b", "c  d", "e"]

scan.rb

def scan(str)
    if str == nil
        []
    else
        data = if str[0] == "'"
            split_quote(str)
        elsif str[0] == " "
            skip_space(str)
        else
            split_space(str) 
        end
        data[0] + scan(data[1]) 
    end
end

def skip_space(str)
    [[], str[1..-1]]
end

def split_space(str)
    head = ""
    tail = nil
    for i in 0..(str.size - 1) do
        x = str[i]
        if x == " "
            tail = str[(i+1)..-1]
            break
        else
            head += x
        end
    end

    [[head], tail]
end


def split_quote(str)
    head = ""
    tail = nil
    for i in 1..(str.size - 1) do
        x = str[i]
        if x == "'"
            tail = str[(i+2)..-1]
            break
        else
            head += x
        end
    end

    [[head], tail]
end