Safe Haskell | Safe-Inferred |
---|---|
Language | Haskell98 |
The virtual machine on which the specifications execute.
Synopsis
- type VM a = StateT Store Effect a
- type Data = Dynamic
- type Loc = Int
- data Scheduler
- data Store
- data ThreadId
- initialStore :: Scheduler -> Store
- alloc :: VM Loc
- emptyLoc :: Loc -> VM ()
- freshThreadId :: VM ThreadId
- finishThread :: ThreadId -> VM ()
- lookupHeap :: Loc -> VM (Maybe Data)
- mainTid :: ThreadId
- printChar :: Char -> VM ()
- readChar :: VM Char
- updateHeap :: Loc -> Data -> VM ()
- updateSoup :: Executable f => ThreadId -> IOSpec f a -> VM ()
- data Effect a
- roundRobin :: Scheduler
- singleThreaded :: Scheduler
- class Functor f => Executable f where
- data Step a
- runIOSpec :: Executable f => IOSpec f a -> Scheduler -> Effect (a, Store)
- evalIOSpec :: Executable f => IOSpec f a -> Scheduler -> Effect a
- execIOSpec :: Executable f => IOSpec f a -> Scheduler -> Store
The Virtual Machine
type VM a = StateT Store Effect a Source #
The VM
monad is essentially a state monad, modifying the
store. Besides returning pure values, various primitive effects
may occur, such as printing characters or failing with an error
message.
Instances
initialStore :: Scheduler -> Store Source #
Primitive operations on the VM
emptyLoc :: Loc -> VM () Source #
The emptyLoc
function removes the data stored at a given
location. This corresponds, for instance, to emptying an MVar
.
freshThreadId :: VM ThreadId Source #
The freshThreadId
function returns a previously unallocated ThreadId
.
finishThread :: ThreadId -> VM () Source #
The finishThread
function kills the thread with the specified
ThreadId
.
lookupHeap :: Loc -> VM (Maybe Data) Source #
The lookupHeap
function returns the data stored at a given
heap location, if there is any.
updateHeap :: Loc -> Data -> VM () Source #
The updateHeap
function overwrites a given location with
new data.
updateSoup :: Executable f => ThreadId -> IOSpec f a -> VM () Source #
The updateSoup
function updates the process associated with a
given ThreadId
.
The observable effects on the VM
The Effect
type contains all the primitive effects that are
observable on the virtual machine.
Sample schedulers
There are two example scheduling algorithms roundRobin
and
singleThreaded
. Note that Scheduler
is also an instance of
Arbitrary
. Using QuickCheck to generate random schedulers is a
great way to maximise the number of interleavings that your tests
cover.
roundRobin :: Scheduler Source #
The roundRobin
scheduler provides a simple round-robin scheduler.
singleThreaded :: Scheduler Source #
The singleThreaded
scheduler will never schedule forked
threads, always scheduling the main thread. Only use this
scheduler if your code is not concurrent.
Executing code on the VM
class Functor f => Executable f where Source #
The Executable
type class captures all the different types of
operations that can be executed in the VM
monad.
Instances
Executable ForkS Source # | |
Executable IORefS Source # | The |
Executable MVarS Source # | |
Executable STMS Source # | |
Executable Teletype Source # | |
(Executable f, Executable g) => Executable (f :+: g) Source # | |
evalIOSpec :: Executable f => IOSpec f a -> Scheduler -> Effect a Source #
The evalIOSpec
function returns the effects a computation
yields, but discards the final state of the virtual machine.
execIOSpec :: Executable f => IOSpec f a -> Scheduler -> Store Source #
The execIOSpec
returns the final Store
after executing a
computation.
Beware: this function assumes that your computation will
succeed, without any other visible Effect
. If your computation
reads a character from the teletype, for instance, it will return
an error.