# `Aether.Eval`
[🔗](https://github.com/joetjen/ichor/blob/v0.3.0/lib/aether/eval.ex#L1)

The semantic half of Aether's front-end: turns an `Aether.Reader.Grammar`
CST into a fully resolved `Aether.Grammar`, with every body already
`Grammar.IR`.

(Not to be confused with `Ichor.Actions.evaluate/5`, which evaluates
*parsed input* through a grammar's own actions -- this evaluates
*grammar source*, already read into a CST by `Aether.Reader`, into
`Grammar.IR`.)

Owns everything that needs more than one definition's worth of
context: predefined-token (`DIGIT`/`ALPHA`/`ALNUM`/`SPACE`/`HEX`)
override-before-use tracking (uses can be implicit -- a POSIX class
item, a regex escape, an auto-spliced default skip token -- which is
exactly why this can't be checked while merely reading syntax),
case-insensitivity resolution, character-class/regex desugaring,
inline-literal auto-promotion to anonymous tokens, `@skip` splicing,
and the final `@root`/`@skip` validation.

# `build`

```elixir
@spec build(Aether.Reader.Grammar.t()) ::
  {:ok, Aether.Grammar.t()} | {:error, Ichor.Error.t()}
```

Builds a fully resolved `Aether.Grammar` from `reader_grammar`.

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