README.md

How to create a Fly project

After installing Fly, it is necessary to follow some steps in order to create a project in Eclipse IDE for DSL:

• Open a new Eclipse runtime. Right click on org.xtext.FLY -> Run as... -> Eclipse application;
• Create a new project in the Fly runtime. New project -> Maven project -> select it.isisLab archetype -> set a name for the project -> Finish;
• Convert the project in a Fly project. Right click on src/main/fly -> New file -> set a filename with a .fly extension -> Finish. After creating a .fly file, Eclipse will prompt about the project conversion. Select yes.

Once the Fly project is created, it is the moment to write your Fly program. A Fly project is divided in two main folders:

• src/main/fly for .fly files;
• src-gen where the Fly generator will compile Fly code in Java code and scripts for deploy and undeploy.

Tips for new developers

When you write a Fly program, it's recommended to follow some rules of thumb in order to avoid the majority of errors:

1. Initialize your variables berfore using them for complex assignments. This will avoid some type parsing errors. Here is an example:

var x = 10
var y = x //Wrong. Fly generator will recognize y variable as variable Object.

var x = 10

var y = 0
y = x    //Right. Fly generator will recognize y variable as Integer.

2. If you have to use data structures in a function, prefer using const instead of passing parameters. This allows to avoid other type parsing errors. Here is an example:

var x = [[0, 1, 2], [3, 4, 5]] //Matrix declaration

func myFunction(x){            //x will be recognized as Integer
  ... some code ...
}


const y = [[0, 1, 2], [3, 4, 5]]

func myFunction2(){            //This won't produce errors 
  var z = y[0][0]
  
  ... some code ...
}