Program Structure and Variables - BrainDump

Unlike C# and Visual Basic.NET, Boo does not require a class to be declared with a static method as the program's entry point. A basic "Hello World" program can be written in a single line:

print "Hello World!"

Here, print is actually a macro. Boo users are free to develop their own macros as substitutes for repetitive code. Using the print macro is the same as calling the built-in print method:

print("Hello World!")

To access a namespace's contents without having to specify the namespace itself, import is used:

import System

Console.WriteLine("Hello World!")

Now let's look at defining variables in Boo. Boo is a statically typed language, so the types of variables are determined at compile-time. Let's define some variables of various types:

name as string = "John Doe"

gender as char = char('m')

married as bool = false

age as int = 35

savings as double = 12345.67

Note how we explicitly assign each variable a type. In some instances, such as when we define but don't immediately initialize a variable, this is required. However, Boo can usually determine the type of a variable at compile-time just by looking at what's assigned to it:

name = "John Doe"

gender = char('m')

married = false

age = 35

savings = 12345.67

Although Boo is a statically typed language, there exists a special type called duck that provides support for duck typing. That is, you're free to use a variable of type duck as you see fit, without the compiler watching your back at compile-time:

x as duck

x = 4

x = "four"

x = false

The above code assigns an integer value to x, followed by a string and then false. Normally, this wouldn't compile, but with Boo's duck typing, it does. The above example is poor, however, since the same effect could be achieved by declaring x as type object. Consider this next example, then, where we use methods associated with specific types:

x as duck

x = 4

x = x.MinValue

x = "string"

x = x.Replace("s", "q")

Note, though, that Boo is still a statically typed language and that duck typing should not generally be used.