A format for expressing an ordered list of integers is to use a comma separated list of either

 individual integers
 Or a range of integers denoted by the starting integer separated from the end integer in the range by a dash, '-'. (The range includes all integers in the interval including both endpoints)
 The range syntax is to be used only for, and for every range that expands to more than two values.
Example

The list of integers:

 -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20
Is accurately expressed by the range expression:

 -6,-3-1,3-5,7-11,14,15,17-20
(And vice-versa).



Task

Expand the range description:

  -6,-3--1,3-5,7-11,14,15,17-20 

Note that the second element above,
is the range from minus 3 to minus 1. 



Related task

   Range extraction


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")