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Whenever you want to get started with a new language (in our case Eiffel) or an Integrated Development Environment (in our case, EiffelStudio), one always tries to run the simplest possible program - one that prints out “Hello World”.
In Java you need
(a) the hello_world.java code
(b) the variable CLASSPATH must be set correctly so that the Java runtime will find your classes and the basic pacakges to compile your program.
In Eiffel you also need
(a) the hello_world.e file with the Eiffel code as well as
(b) a *.ecf file that tells the Eiffel compiler (called ec) where to find your files as well as all the libraries (such as the base library) that your code will be using.
Here are the contents of hello_world.e:
class HELLO_WORLD create make feature make do print("Hi World!") end end
- Note1: ensure that the file name is “hello_world.e” and the class name in the file is HELLO_WORLD. Eiffel is case insensitive. However, the convention is to write class names in CAPITAL letters.
- Note2: On Windows, you might want to put “io.read_line” after the print statement. Semi-colons are not needed between lines (to indicate sequencing).
Command line (''ec15.12'')
To compile your program from the command line, use
ec15.12 hello_world.e
On Prism (Linux), we have renamed the command line compiler (“ec”) to '“ec15.12”, as we are using EiffelStudio version 15.12.
[On your own install in Linux/Windows/MacOs, you may be prompted to precompile. Answer Yes.]
On Windows/MacOs, the command line will just be “ec”. On Windows, use the EiffelStudio 15.12 Command Prompt (available from the Start menu).
When you invoke ec on a single source file such as hello_world.e, the compiler will generate the ecf file for you (hello_world.ecf). ECF files specify which libraries will be used. The Base library is always included.
To execute the program:
cd EIFGENs/hello_world/W_code ./hello_world
You can obtain a finalized executable that can be deployed by any user (without the need for the EiffelStudio environment) by:
ec15.12 -c_compile -finalize -config hello_world.ecf
The Eiffel program is translated to C, and the C program is compiled to executable machine code (that does not need a virtual machine to run it). To execute the program:
cd EIFGENs/hello_world/F_code ./hello_world
The above executable should print out “Hi world”. This executable is all you need to run the program on any other Linux machine of the same architecture.
- Note: If you are using the command line under Windows, then the compiler is ec (not ec15.12). Use the Eiffel 15.12 command prompt (available from the Start menu). Alternatively,ensure that:
C:\Program Files\Eiffel Software\EiffelStudio 15.12 GPL\studio\spec\windows\bin
is on your PATH variable.
IDE (estudio15.12)
You can invoke the EiffelStudio IDE on the above project as follows:
> estudio15.12 &
(On your own install, it is just estudio).
When you start a new project on the IDE, you can use the Wizard to generate an ECF file automatically. If you already have a project with ECF file foo.ecf, then you can start from the command line as follows:
estudio15.12 foo.ecf &.
(The ampersand at the end causes the EStudio process to run in the background, leaving the terminal free for further commands.)
Read EStudio documentation for more details.
