Safe Haskell	Safe-Inferred
Language	Haskell2010

Build.SelfTracking

Description

This module defines two different strategies of self-tracking, based around the idea of storing task descriptions that can be parsed into a Task.

For Monad it works out beautifully. You just store the rule on the disk, and depend on it.
For Applicative, we generate a fresh Task each time, but have that Task depend on a fake version of the rules. This is a change in the Task, but it's one for which the standard implementations tend to cope with just fine. Most applicative systems with self-tracking probably do it this way.

Synopsis

data Key k
- = Key k
- | KeyTask k
data Value v t
- = Value v
- | ValueTask t
selfTrackingM :: forall k v t. (t -> Task Monad k v) -> Tasks Monad k t -> Tasks Monad (Key k) (Value v t)
selfTrackingA :: (t -> Task Applicative k v) -> (k -> t) -> Tasks Applicative (Key k) (Value v t)

Documentation

data Key k Source #

We assume that the fetch passed to a Task is consistent and returns values matching the keys. It is possible to switch to typed tasks to check this assumption at compile time, e.g. see Build.Task.Typed.

Constructors

Key k
KeyTask k

data Value v t Source #

Constructors

Value v
ValueTask t

selfTrackingM :: forall k v t. (t -> Task Monad k v) -> Tasks Monad k t -> Tasks Monad (Key k) (Value v t) Source #

A model for Monad, works beautifully and allows storing the key on disk.

selfTrackingA :: (t -> Task Applicative k v) -> (k -> t) -> Tasks Applicative (Key k) (Value v t) Source #

The applicative model requires every key to be able to associate with its environment (e.g. a reader somewhere). Does not support cutoff if a key changes.