Ruby Array#sort how it knows that the block should sort in ascending or descending order

A related question is already available at https://stackoverflow.com/a/11427868/936494 but what I want to understand is

when using

a.sort { |x, y| x <=> y }

how it knows that this block should sort in ascending order and similarly when using

a.sort { |x, y| y <=> x }

how it knows that this block should sort in descending order? I am puzzled because both the blocks uses the spaceship operator and it is expected to return following during each comparison in case of a.sort { |x, y| x <=> y }

• -1 if x < y
• 0 if x == y
• 1 if x > y

and following during each comparison in case of a.sort { |x, y| y <=> x }

• -1 if y < x
• 0 if y == x
• 1 if y > x

Now let’s take an example array:

2.3.2 :023 > a = [ "d", "a", "e", "c", "b" ]
=> ["d", "a", "e", "c", "b"]

When we sort it using a.sort { |e1, e2| p [e1, e2]; e1 <=> e2 } following is the result:

["d", "a"] (cmp result: 1)
["c", "b"] (cmp result: 1)
["e", "b"] (cmp result: 1)
["e", "c"] (cmp result: 1)
["a", "b"] (cmp result: -1)
["d", "b"] (cmp result: 1)
["d", "c"] (cmp result: 1)
["d", "e"] (cmp result: -1)
=> ["a", "b", "c", "d", "e"]

Now in this case how it knows that “a” is to be put 1st, then “b”, then “c”, etc?

Similarly when we sort it using a.sort { |e1, e2| p [e2, e1]; e2 <=> e1 } following is the result:

["a", "d"] (cmp result: -1)
["b", "c"] (cmp result: -1)
["c", "e"] (cmp result: -1)
["e", "d"] (cmp result: 1)
["c", "d"] (cmp result: -1)
["c", "a"] (cmp result: 1)
["b", "a"] (cmp result: 1)
=> ["e", "d", "c", "b", "a"]

So in this case how it knows that “e” is to be put 1st, then “d”, then “c”, etc? And that considering the fact that the comparisons of two elements in both the blocks should return 1, 0 or -1?