# `mix localize.unit.gen_conversions`
[🔗](https://github.com/elixir-localize/localize/blob/v1.2.0/lib/mix/tasks/localize.unit.gen_conversions.ex#L1)

Generates a self-contained Elixir module that converts units to their
base units, with no dependency on Localize at all.

The generated module is intended for targets where compiling Localize
is too expensive — Nerves devices and other embedded builds, where the
~200 modules of the full library cost more compile time than the
project itself. Localize stays on the developer's machine as the
generator; the emitted file is committed and compiles in milliseconds.

The generated module accepts every unit `Localize.Unit` accepts, so
there is nothing to select and no arguments to give. That covers the
155 units CLDR defines a conversion for, every SI-prefixed form of
them, every power (`square-`, `cubic-`, `pow4-`), and every compound
built with `-per-` or by juxtaposition — `newton-meter`,
`kilogram-square-meter`, `newton-meter-second-per-radian`,
`millitherm-us-per-square-second`. The accepted set is unbounded, so it
is not tabulated: identifiers are parsed and reduced to a canonical
base unit at call time.

Parity with `Localize.Unit` is structural rather than maintained.
Localize's own unit parser is written as a NimbleParsec template, and
`mix nimble_parsec.compile` expands it into plain Elixir functions with
no runtime dependency. That expansion is inlined into the generated
file, so the emitted module parses identifiers with the same code
Localize does — there is no second grammar to keep in step.

Base units are canonical: `resolve/1` returns the same base identifier
`Localize.Unit.BaseUnit.base_unit/1` returns, with the same factor.

### Arguments

* `--module` is the name of the module to generate, for example
  `Robot.Units`. The default is `Units`.

* `--output` is the path to write. The default is derived from the
  module name under `lib/`.

### Returns

* `:ok` after writing the generated file.

### Examples

    $ mix localize.unit.gen_conversions
    * creating lib/units.ex
      155 units, 655 spellings, every prefixed and compound form of them

    $ mix localize.unit.gen_conversions --module Robot.Units
    * creating lib/robot/units.ex

    $ mix localize.unit.gen_conversions --module Robot.Units --output lib/units.ex

---

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