pullInt = function(chars)
    numstr = chars.pull
    while chars and chars[0] != "," and chars[0] != "-"
        numstr = numstr + chars.pull
    end while
    return val(numstr)
end function

expandRange = function(s)
    result = []
    chars = s.split("")
    while chars
        num = pullInt(chars)
        if not chars or chars.pull == "," then
            result.push num
        else
            result = result + range(num, pullInt(chars))
            chars.pull  // skip "," after range
        end if
    end while
    return result
end function

print expandRange("-6,-3--1,3-5,7-11,14,15,17-20")