EO (stands for Elegant Objects or ISO 639-1 code of Esperanto) is an object-oriented programming language based on π-calculus. We're aware of popular semi-OOP languages and we don't think they are good enough, including: Java, Ruby, C++, Smalltalk, Python, PHP, C#. All of them have something we don't tolerate:
- types (why?)
- static/class methods or attributes (why?)
- classes (why?)
- implementation inheritance (why?)
- mutability (why? and why not?)
- NULL (why?)
- global scope (why?)
- type casting (why?)
- reflection (why?)
- scalar types and data primitives
- annotations (why?)
- operators
- traits and mixins (why?)
- flow control statements (
for,while,if, etc) - syntactic sugar (why?)
First, install Java SE, npm. Then, you install eoc:
npm install -g eolang@0.28.0Then, start with a simple EO program in the app.eo file:
# Just prints hello.
[args] > app
QQ.io.stdout > @
"Hello, world!\n"
Compile it like this (may take up to a minute or so):
eoc --easy linkThen, run it:
eoc --easy --alone dataize appYou should see "Hello, world!" printed.
In the example above, we create a new
abstract object
named app, which has got a single attribute named @. The object
attached to the attribute @ is a copy of the object stdout with
a single argument "Hello, world!". The object
stdout is also
abstract.
It can't be used directly, a copy of it has to be created,
with a few requirement arguments provided.
This is how a copy of the object stdout is made:
QQ.io.stdout
"Hello, world!\n"
The indentation in EO is important, just like in Python. There have to be two spaces in front of the line in order to go to the deeper level of nesting. This code can also be written in a "horizontal" notation:
QQ.io.stdout "Hello, world!"
Moreover, it's possible to use brackets in order to group arguments and avoid
ambiguity. For example, instead of using a plain string "Hello, world!"
we may want to create a copy of the object stdout with a more complex
argument: a copy of the object sprintf:
# Says hello to Jeff.
[] > app
QQ.io.stdout > @
QQ.txt.sprintf
"Hello, %s!"
* "Jeffrey"
Here, the object sprintf is also
abstract.
It is being copied with two arguments: "Hello, %s!" and "Jeffrey".
This program can be written using horizontal notation:
+alias org.eolang.io.stdout
+alias org.eolang.txt.sprintf
# Also says hello to Jeff.
[] > app
(stdout (sprintf "Hello, %s!" (* "Jeffrey"))) > @
The special attribute @ denotes an object that is being
decorated.
In this example, the object app decorates the copy of the
object stdout and through this starts to behave like
the object stdout: all attributes of stdout become the
attributes of the app. The object app may have its own
attributes. For example, it's possible to define a new abstract object
inside app and use it to build the output string:
# Says hello to Jeff.
[] > app
QQ.io.stdout (msg "Jeffrey") > @
[name] > msg
QQ.txt.sprintf "Hello, %s!" (* name) > @
Now, the object app has two "bound" attributes: @ and msg. The attribute
msg has an abstract object attached to it, with a single "free" attribute
name.
This is how you iterate:
# Multiplication table.
[args] > app
malloc.for > @
0
[x] >>
seq > @
*
x.put 2
while
x.as-number.lt 6 > [i]
[i] >>
seq > @
*
QQ.io.stdout
QQ.txt.sprintf
"%d x %d = %d\n"
*
^.x
^.x
^.x.as-number.times ^.x
^.x.put
^.x.as-number.plus 1
true
This code will print this:
2 x 2 = 4
3 x 3 = 9
4 x 4 = 16
5 x 5 = 25
Got the idea?
This is our EBNF, of EO language:
This is the EBNF of π-calculus:
The images were auto-generated. It's better to use ebnf/Eo.svg and ebnf/Phi.svg.
Join our Telegram group.
Watch video about EOLANG basics.
Read our blog, especially the section with recently published papers.
Learn XMIR, a dialect of XML, which we use to represent EO program: XSD is here, full specification is here.
See the full collection of canonical objects: objectionary.
Take a look how we use EO as an Intermediary Representation (IR) in Polystat, a polyglot static analyzer.
Play with more examples here.
Read about integration with Maven, here.
This is how many milliseconds were spent on different
XSL stylesheets during the execution of mvn install of
the eo-runtime module:
to-java.xsl 68374 32.24%
add-refs.xsl 24572 11.59%
set-locators.xsl 12709 5.99%
tests.xsl 10906 5.14%
rename-tests-inners.xsl 9867 4.65%
add-probes.xsl 6233 2.94%
resolve-aliases.xsl 6178 2.91%
classes.xsl 5927 2.79%
package.xsl 5883 2.77%
add-default-package.xsl 5780 2.73%
explicit-data.xsl 5612 2.65%
vars-float-up.xsl 5529 2.61%
cti-adds-errors.xsl 5062 2.39%
normalize-bytes.xsl 4395 2.07%
expand-qqs.xsl 4345 2.05%
atoms-with-bound-attrs.xsl 4342 2.05%
The results were calculated in this GHA job on 2024-12-20 at 11:57, on Linux with 4 CPUs. The total is 212095 milliseconds. We show only the first 16 most expensive XSL stylesheets.
You can run this benchmark locally with the following commands.
First, to generate the measures.csv file:
mvn clean install --errors --batch-mode -Deo.xslMeasuresFile=measures.csvThen, to generate the report:
awk -F ',' '{ a[$1]+=$2; s+=$2; } END { for (k in a) \
printf("%s.xsl\t%d\t%0.2f%%\n", k, a[k], 100 * a[k]/s)}' \
eo-runtime/measures.csv | sort -g -k 2 | tail -r | column -t | head "-16"Fork repository, make changes, then send us
a pull request.
We will review your changes and apply them to the master branch shortly,
provided they don't violate our quality standards. To avoid frustration,
before sending us your pull request please run full Maven build:
mvn clean install -PquliceYou will need Maven 3.3+ and Java 11+ installed.
We are using the YourKit Java Profiler to enhance the performance of EO components:
