Build.Task.Monad

Monadic tasks, as used by Excel, Shake and other build systems. Dependencies of monadic tasks can only be discovered dynamically, i.e. during their execution.

Documentation

track :: Task Monad k v -> (k -> v) -> (v, [k])

Execute a monadic task on a pure store k -> v, tracking the dependencies.

trackM :: forall m k v. Monad m => Task Monad k v -> (k -> m v) -> m (v, [k])

Execute a monadic task using an effectful fetch function k -> m v, tracking the dependencies.

isInput :: forall k v. Tasks Monad k v -> k -> Bool

Given a description of tasks, check if a key is input.

compute :: Task Monad k v -> (k -> v) -> v

Run a task with a pure lookup function.

partial :: Task Monad k v -> Task Monad k (Maybe v)

Convert a task with a total lookup function k -> m v into a task with a partial lookup function k -> m (Maybe v). This essentially lifts the task from the type of values v to Maybe v, where the result Nothing indicates that the task failed because of a missing dependency.

exceptional :: Task Monad k v -> Task Monad k (Either e v)

Convert a task with a total lookup function k -> m v into a task with a lookup function that can throw exceptions k -> m (Either e v). This essentially lifts the task from the type of values v to Either e v, where the result Left e indicates that the task failed because of a failed dependency lookup, and Right v yeilds the value otherwise.