# `mix schooner.expand`
[🔗](https://github.com/ausimian/schooner/blob/1.2.0/lib/mix/tasks/schooner.expand.ex#L1)

Prints what a Scheme script's macros expand to, with
`Schooner.expand/3` and `Schooner.Pretty`, without running it.

    $ mix schooner.expand -e "(when (> n 0) (go n))"
    (if (> n 0) (begin (go n)))

Give either a file or, with `-e`, the source itself. The expanded
top-level forms are printed one after another, with a blank line
between them. An identifier a macro introduces is printed with a
number, such as `tmp·1`, so it can be told apart from the script's
own `tmp`.

## Options

  * `-e`, `--eval SOURCE` — expand `SOURCE` instead of a file.
  * `--env Mod.fun` — expand against the `Schooner.Environment`
    returned by the zero-arity function `Mod.fun`. Without it, the
    environment is the one configured with

        config :schooner, :tooling_environment, {Mod, :fun, args}

    and without that, every standard library, all imported: the
    surface `Schooner.run/1` gives a script that imports nothing.
    The environment decides which macros are in scope, so prefer
    your application's real one.
  * `--once` — expand each macro use that is not inside another
    macro use once, leaving the macro uses in its output as they
    are.
  * `--trace` — before the result, print each macro use expanded,
    in order: its number, the macro's name and the location of the
    use, then the use and, after `=>`, what it expanded to.

        $ mix schooner.expand -e "(unless ok (fail))" --trace
        [1] unless at 1:1
            (unless ok (fail))
         => (if ok (begin) (begin (fail)))

        (if ok (begin) (begin (fail)))

  * `--plain` — print renamed identifiers by their names alone
    (`tmp`).
  * `--width N` — the line width to fit forms in. Defaults to 80.

When the script can't be read or expanded, the task prints the error
and exits with status 1.

---

*Consult [api-reference.md](api-reference.md) for complete listing*