Ruby threads order of output?

Question

I'm reading about Ruby Threads (I've never used Ruby before), and I'm surprised about the following code:

t1 = Thread.new { print "w"; Thread.pass; print "a"}
t2 = Thread.new { print "e"; Thread.pass; print "l"}
t1.join
t2.join

The book said that always will show "weal" and I don't understand why, because if they are real threads (as in other languages), it is not ensured that "w" will print before "e".

Thank you for your answers!

Answer 1

Change the book or read it with care. You are of course right, the only guarantee is that a will show after w etc.

I have just tested your code and here are results after 10 runs:

weal
weal
ewal
wela
wael
wael
wela
ewla
ewla
weal