The ``Hello World!'' program will be written in a directory called hello/ and place the client library in a subdirectory hello/lib/:
% mkdir hello
% cd hello
% mkdir lib
The first step is to write a SIDL file. Recall that SIDL is an interface definition language (IDL) that describes the calling interface for a scientific library. It is used by the Babel tools to generate glue code that hooks together different programming languages. A complete description of SIDL can be found in Chapter 5.
For this particular application, we will write a SIDL file that contains a class World in a package Hello. Method getMsg() in class World returns a string containing the traditional computer greeting. Using your favorite text editor, create a file called hello.sidl in the hello/ directory containing the following:
package Hello version 1.0 { class World { string getMsg(); } }
The package statement provides a scope (or namespace) for class World, which contains only one method, getMsg(). The version clause of the statement identifies this as version 1.0 of the Hello package.