There's often a requirement in a program to see if one value is between two others, and in most languages you'll write that as as double condition:
if (n >= 5 && n <= 8) printf("Yesssss!\n");
in C or C++, for example.
Some languages give you further options / methods you can use to test for values between two others - usually they're the object oriented languages where additional operators can be defined as methods. In other words - when the authors of he language ran out of special symbols, they started to use words! Here is a use of the
between? method in Ruby:
if k.between?(5,8)
Another requirement is to see if a value is present in a list / array / collection. And in languages such as C you'll write that as a loop, checking each item of the list in turn and using a
break go get out of the loop if and when you find the item you're looking for.
Looking for an item in a list is such a common requirement that many of the object oriented languages have defined methods which let you do the test in a single line, hiding (encapsulating) the loop that's actually still going to be run within the class code. So in Ruby you cab simply write:
if [2,3,5,6,7].include?(k)
There's a new demonstration of each of these, in the context of a complete program,
[here] on our web site. I'm running a private Ruby course this week. Public courses - see
[here].
(written 2011-04-18, updated 2011-04-19)
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