# `Skuld.Comp.ITotalLinearHandler`
[🔗](https://github.com/mccraigmccraig/skuld/blob/main/lib/skuld/comp/i_total_linear_handler.ex#L1)

Behaviour for effect operation handlers that are provably total and linear.

A handler is **total** if it produces a value for every possible input —
it never diverges, never throws an exception, and never raises an effect.
A handler is **linear** if it has use-once semantics — the handler always
either returns normally or the computation ends.

When both properties hold, the `comp` macro can emit an optimised call
path that skips continuation allocation and CPS indirection:

    {value, env2} = handler.(args, env)
    comp2 = f.(value)
    call(comp2, env2, k)

## Example

    defmodule MyTotalLinearEffect do
      @behaviour Skuld.Comp.ITotalLinearHandler

      @total [:get]
      @linear [:get]

      @impl Skuld.Comp.ITotalLinearHandler
      def handle(:get, env) do
        {Env.get_state!(env, @key), env}
      end
    end

## See Also

- `Skuld.Comp.IHandle` — the general 3-arity handler behaviour

# `handle`

```elixir
@callback handle(args :: term(), env :: Skuld.Comp.Types.env()) ::
  {Skuld.Comp.Types.result(), Skuld.Comp.Types.env()}
```

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