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Hello world!

We start by specifying the modelling boundary. We do so by specifying the world. The absolute minimal ESL specification you can write is therefore:

world.esl
1
2
world
  empty
world.esl
1
2
3
4
# ---8<--- [start:highlight]
world
  empty
# ---8<--- [end:highlight]

Thus introducing two new keywords:

  • world: The modelling boundary, can only occur once in a ESL specification. We assume nothing exists outside of the world.
  • empty: When we want to specify something without any further information, we write empty to signal this.

Note

All code blocks in this tutorial come in two pairs. The first is the Highlight, which usually is an example of the newly added 'thing'. The second one is the entire File, which pretty much always is world.esl for the duration of the tutorial.

Compiling a specification

In order to compile this specification and check for any errors, make sure you have RaESL or another compatible compiler installed and run raesl compile world.esl on your command line while you are in the same directory as world.esl.

For more advanced compilation setups with multiple files and/or directories, take a look at raesl compile --help for the latest command line options.

Tip

By convention, we name the file containing the world definition world.esl so that it's always easy to find.

Tip

Although we use a certain spacing style when writing ESL specifications, we only do this for readability.

The parser and compiler ignore any indentation.

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