Module Development

A module is simply an .eng file that can be loaded by another program.

Create a module

Create math_helpers.eng:

Define a function called square that takes x and returns x multiplied by x.

Define a function called cube that takes x and returns x multiplied by x multiplied by x.

Use the module

Create main.eng in the same directory:

Import math_helpers.

Print Run square with 5.
Print Run cube with 3.

Run:

eng run main.eng

Selective imports

Instead of importing every global from a module:

From math_helpers use square.

Now square is available to the importing program.

Module isolation

The loader executes the imported source in a separate VM, collects its globals, and copies those values into the importer. This is why module execution does not simply continue inside the caller's current local scope.

Circular imports

If module A imports module B and B eventually imports A, the loader detects the module already being loaded and reports a circular-import error.

Search paths

Set ENGLING_PATH to add module directories outside the current project.

For example, on a Unix-like shell:

export ENGLING_PATH="$HOME/.engling/modules"

Then a module can be resolved from that directory.