From Rosetta Code
This programming language may be used to instruct a computer to perform a task.
Official website
Garbage collected: Yes
Parameter passing methods: By value
Type safety: Safe
Type strength: Strong
Type compatibility: Duck
Type expression: Explicit
Type checking: Dynamic
See Also:
Listed below are all of the tasks on Rosetta Code which have been solved using E.
Your Help Needed
If you know E, please write code for some of the tasks not implemented in E.

E is a programming language designed around object-capability security and event-loop concurrency, in order to support creation of highly robust and secure programs.

Using the Java implementation of E, Java libraries can be used from E code, and its REPL (e.g. Creating a Window).

Trying E

The current recommended E implementation ("E-on-Java") may be downloaded from

To run an E program:

$ rune program.e

To get a REPL (aka prompt, shell, interactive interpreter):

$ rune

An online REPL is also available at Rosetta Code IRC or #erights on

Syntax of examples

While most of the examples on Rosetta Code are E expressions (programs), some may be written like this:

? expression
# value: print representation

This is both the format of a transcript at an E REPL, and the format employed by Updoc, a test framework for E. “?” is a prompt for user input (“>” indicates multi-line input) and “# foo:” indicates responses.

  • # value: the return value of the expression, printed
  • # problem: an exception thrown by evaluation of the expression
  • # syntax error: an exception thrown by parsing of the expression
  • # stdout: or # stderr: text written to the stdout or stderr streams. It is typically only used in test scripts and not in ordinary interactive sessions.

To try out these examples for yourself, just install E and run the rune command to get the “?” prompt. Multi-line input is automatic for unbalanced brackets/parens and can be indicated in other cases by a trailing backslash.

See Also


This category has the following 3 subcategories, out of 3 total.

Pages in category "E"

The following 269 pages are in this category, out of 269 total.