Files

A file should hold names that belong together. A small file is easier to scan than a large mixed file.

let total := 42;
total;

Put receipt rules near receipt data. Put route rules near route data. Do not make one file a drawer for every helper.

A file is like one page in a binder. If the page needs many unrelated headings, it likely wants to become more than one page.

Use exports only for names another file needs.

File boundary

One file should have one clear reason to change.

export let defaultServer := { host := "localhost", port := 8080 };

export let defaultPort := defaultServer.port;

Keep private helper names private. Export values and functions that other files actually use.

Split point

Split a file when it mixes unrelated data, unrelated effects, or unrelated public APIs. A file named server.ms should not also own payment rules.