Skuld.Comp.IHandle behaviour (skuld v0.2.3)

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Behaviour for effect operation handlers.

Implementing this behaviour provides:

  • LSP autocomplete for the handle/3 callback signature
  • Compile-time warnings if the callback is missing or has wrong arity
  • Public handle/3 function that can be referenced as &Module.handle/3

Example

defmodule MyEffect do
  @behaviour Skuld.Comp.IHandle

  @impl Skuld.Comp.IHandle
  def handle(%Get{}, env, k) do
    value = Env.get_state(env, @state_key)
    k.(value, env)
  end

  @impl Skuld.Comp.IHandle
  def handle(%Put{value: v}, env, k) do
    new_env = Env.put_state(env, @state_key, v)
    k.(:ok, new_env)
  end
end

# Install handler:
comp |> Comp.with_handler(MyEffect, &MyEffect.handle/3)

See Also

Summary

Callbacks

handle(args, env, k)

Handle an effect operation.

Callbacks

handle(args, env, k)

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

Handle an effect operation.

Receives:

  • args - the operation arguments (e.g., %Get{}, %Put{value: v})
  • env - the current environment
  • k - the continuation to invoke with the result

Must return {result, env} - either by calling k.(value, env) or by returning a sentinel like {%Skuld.Comp.Throw{}, env}.