Hello World (E)

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E is an object-oriented language for secure distributed programming. This article presents a simple example of E's basic syntax. To run this example, you will need to install E - see ERights.org, the E language website, for more information.

This is a simple E program that prints the classic "Hello World!" string to the console, then prints the integers 1 through 10 using a simple for loop.

Printing a greeting is as simple as

<<print greeting>>=
println("Hello World!")

Printing the first 10 integers can be implemented (using a range) like this:

<<print first ten integers>>=
for i in 1..10 {
  println(i)
}

Presently, E is primarily used as a scripting language via the rune interpreter. To complete the E script, we add a shell declaration which indicates the script should be run using rune, and a pragma.syntax line to define which version of the E language we are assuming:

<<hellowworld.e>>=
#!/usr/bin/env rune
pragma.syntax("0.9")
print greeting
print first ten integers

The script will also work on platforms that don't have a Unix-style shell (e.g. Windows), but must be invoked in a more roundabout fashion:

java -jar %EHOME%\e.jar --rune helloworld.e

where %EHOME% is the directory in which E was installed.

Regardless of which way helloworld.e is run, the output should look like this:

$ ./helloworld.e 
Hello World!
1
2
3
4
5
6
7
8
9
10

References

• ERights.org - the E language website
• Wikipedia entry on the E programming language

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