Nano

A minimal alternative core library for the Crystal programming language.

What

Nano is an alternative core library that doesn't need a GC and tries to bring some features from stdlib that don't allocate memory behind your back, yet still leverage structs, generics and exceptions that don't raise but will panic (print a backtrace & exit the current thread or program).

The initial intent was to have a minimal interface to implement a GC, making sure the stdlib won't try to allocate... which would use the GC (oops).

You can use it to write programs like you would C programs, or write a C library. You may even use it to start programmming microcontrollers (e.g. Arduino, RP2040).

How

The crystal compiler allows to configure an alternate prelude (a simple crystal file) that will be loaded instead of the default prelude that will load everything from the official core library. The compiler even ships an empty prelude that only defines a main function and nothing more.

That empty prelude is very bare metal. Only the few compiler intrinsics are available, that is almost nothing but basic arithmetic, pointers and support for literals.

Nano is an attempt to bring back some niceties from the stdlib, with no GC, no hidden allocations. Pointer#malloc is available but you know when it's called, why it is, and are responsible to clean up the memory (or not).

Usage

Add the nano shard:

dependencies:
  nano:
    github: ysbaddaden/nanolib.cr
    branch: main

Then use nano as your prelude:

$ crystal run app.cr --prelude=nano --release

Alternatively you can write your own prelude and only require the bits of nano you want. See src/nano.cr for example. This is currently required for microcontrollers.

For running tests and specs, you might be interested in microtest.

License

Distributed under the Apache 2.0 license.