# `Grammar.GLR.Runtime`
[🔗](https://github.com/joetjen/ichor_runtime/blob/v0.6.0/lib/grammar/glr/runtime.ex#L1)

The GSS-driving shift-reduce/fork loop itself, shared by the
interpreted `Grammar.GLR` (which wraps a `Grammar.LRTable`'s plain
action/goto maps into closures) and `Grammar.Native.GLR` (which
passes compiled per-state functions instead) -- extracted so both
reuse the exact same, already-proven algorithm. The graph-structured
stack itself (node merging, multi-path reduce enumeration --
`Grammar.GLR.GSS`) is inherently a runtime, input-driven data
structure that can't compile away no matter which engine calls into
it; only *how a caller looks up actions/goto for a state* varies.

# `action_fn`

```elixir
@type action_fn() :: (Grammar.LRTable.state_id(), atom() ->
                  [Grammar.LRTable.action()])
```

# `build_fn`

```elixir
@type build_fn() :: (Grammar.LRTable.Production.t(),
               [Grammar.LRTable.Captures.entry()],
               tuple() ->
                 Ichor.Capture.raw_captures())
```

Builds one reduction's captures: `Grammar.LRTable.Captures.build/3`, or `Ichor.Syntax.Record.reduced/3` for a lossless parse.

# `goto_fn`

```elixir
@type goto_fn() :: (Grammar.LRTable.state_id(), atom() ->
                Grammar.LRTable.state_id() | nil)
```

# `run`

```elixir
@spec run(
  action_fn(),
  goto_fn(),
  %{required(non_neg_integer()) => Grammar.LRTable.Production.t()},
  Grammar.LRTable.state_id(),
  atom(),
  tuple(),
  build_fn()
) ::
  {:ok, non_neg_integer(), Ichor.Capture.raw_captures()}
  | {:error, Ichor.Error.t()}
```

Runs the GSS shift-reduce/fork loop over `stream`, starting from
`start_state`, dispatching every lookup through `action_fn`/`goto_fn`.

`build` builds each reduction's captures. A lossless parse passes
`Ichor.Syntax.Record.reduced/3`, so the rules' records travel with
them, and the run picks the same derivation either way: a surviving
ambiguity is broken by provenance, which `build` never touches.

---

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