Austin Ziegler wrote
>  you can also do:
>
>   puts "yes" if x.between?(-5, 9)
>   puts "yes" if (-5..9).include?(x)

But that's not as readable as  -5 < x < 9, which is how it is written
for humans in algebra.

In Icon, comparisons succeed or fail, they don't return true or false.
So it works this way (if x==0):
(-5 < 0 )  succeeds and produces 0
(0 < 9 ) succeeds and produces 9

1 < x < 9
(1 < 0) fails

-5 < x < -15
(-5 < 0 ) succeeds and produces 0
(0 < -15 ) fails

So in Icon, a < x < b means exactly what it does in algebra.

Matz and many Ruby gurus think that Ruby incorporates the best
features of preceding languages (e.g., Awk, Perl, Python, Smalltalk).
But how many of these people ever used Icon?