It may surprise you to know that you have already seen several
class definitions in this tutorial. If you have written a program in
Pike, you have also written a class. This is because in Pike, programs
and classes are the same, and the terms program and
class are sometimes used as synonyms.
A Pike program in a file is a class definition. The methods that
you have defined in the file are the methods of the class, and the
global variables (that is, the variables defined outside the methods)
are the member variables. If you like, you can imagine that the file
has an implicit "class { }" around the code. But it would be
bothersome if we had to put every little class in its own file, so we
also have the "class { }" notation.
To create the equivalent of the class animal, which we
defined above, we would need a file with the following contents. The
file name can be "animal.pike", but any name will work.
string name;
float weight;
void create(string n, float w)
{
name = n;
weight = w;
}
void eat(string food)
{
write(name + " eats some " + food + ".\n");
weight += 0.5;
}
We can't use a string as a type name, so the file name won't work
as a data type:
"animal.pike" my_dog; // Doesn't work at all.
Instead, we must let Pike read and compile the file, making a
program (or class, if you prefer that term, but the data
type is program) of it, and then we put that program in a
constant:
constant animal = (program)"animal.pike";
Now you can use animal as the class name, just as
before:
animal piglet = animal("Piglet", 6.3);
