# Surface STLC


The STLC examples build a source language incrementally over the HOAS
checker. Each child page introduces one extension, with the full source
available under `examples/stlc/`.

## Layered surfaces

The core surface defines functions and application. Later examples
import that vocabulary and extend it with products, sums, recursive
lists, refinements, and diagnostics.

```nix
core = import ./core.nix { inherit fx lib; };
sumsProducts = import ./sums-products.nix { inherit fx lib core; };
recursiveLists = import ./recursive-lists.nix { inherit fx lib core; };
refinementsDiagnostics = import ./refinements-diagnostics.nix {
  inherit fx lib core;
};
```

## More walkthroughs

- [STLC Core Surface](/nix-effects/surface-examples/stlc/core)
- [STLC Sums and Products](/nix-effects/surface-examples/stlc/sumsProducts)
- [STLC Recursive Lists](/nix-effects/surface-examples/stlc/recursiveLists)
- [STLC Refinements and Diagnostics](/nix-effects/surface-examples/stlc/refinementsDiagnostics)