Ruby has three kinds of variables, one kind of constant and exactly two pseudo-variables. The variables and the constants have no type. While untyped variables have some drawbacks, they have many more advantages and fit well with ruby's quick and easy philosophy.
Variables must be declared in most languages in order to specify their type, modifiability (i.e., whether they are constants), and scope; since type is not an issue, and the rest is evident from the variable name as you are about to see, we do not need variable declarations in ruby.
The first character of an identifier categorizes it at a glance:
The only exceptions to the above are ruby's pseudo-variables:
self, which always refers to the currently executing
nil, which is the meaningless value assigned
to uninitialized variables. Both are named as if they are local
self is a global variable maintained by
the interpreter, and
nil is really a constant. As
these are the only two exceptions, they don't confuse things too
You man not assign values to
main, as a
self, refers to the top-level object: