MIT licensed by Marcellus Siegburg
Maintained by [email protected]
This version can be pinned in stack with:call-alloy-,3486

Module documentation for

call-alloy Haskell CI

This is a simple library to call Alloy given a specification. This package installs a simple Java Library to make an API call to the Alloy Library. Alloy is installed (as JAR file) alongside this library as well.


  • Java Runtime Environment: There is currently no warning if you have not set up any Java Runtime Environment. However, you will get runtime errors if it is not available when a call to Alloy happens. If you want to force a check, perform the test cases.

Please note

The Java interface to get Alloy instances as well as the Alloy Jar file are installed together with this library using usual cabal means (data directory).

The library in action

This is a basic description on how to use the library.

A specification example

Consider this Alloy specification of a simple Graph:

abstract sig Node {
  flow : Node -> lone Int,
  stored : one Int
} {
  stored >= 0
  all n : Node | some flow[n] implies flow[n] >= 0
  no flow[this]

fun currentFlow(x, y : one Node) : Int {
  let s = x.stored, f = x.flow[y] | s < f implies s else f

pred withFlow[x, y : one Node] {
  currentFlow[x, y] > 0

pred show {}

run withFlow for 3 Int, 2 Node

The graph is consisting of Nodes, which might have some goods stored and may deliver them to other Nodes (via flow). Nodes do not have flow to themselves. The currentFlow is the minimum between the flow from the starting Node to the end Node and the currently stored goods at the starting Node (note: intermediate Nodes are not allowed). We call two Nodes x and y withFlow if currentFlow from x to y is greater than 0. We restrict our search to 3-Bit signed Int values and 2 Nodes.

An instance example

Calling Alloy using getInstances and the above program could return the following (abbreviated) instance:

[(Signature {
    scope = Nothing,
    sigName = "$withFlow_x"
  Entry {
    annotation = Just Skolem,
    relation = fromList [
      ("",Single (fromList [Object {objSig = "Node", identifier = 1}]))
 (Signature {
    scope = Nothing,
    sigName = "$withFlow_y"
  Entry {
    annotation = Just Skolem,
    relation = fromList [
      ("",Single (fromList [Object {objSig = "Node", identifier = 0}]))
 (Signature {
    scope = Just "this",
    sigName = "Node"
  Entry {
    annotation = Nothing,
    relation = fromList [
      ("",Single (fromList [
        Object {objSig = "Node", identifier = 0},
        Object {objSig = "Node", identifier = 1}
      ("flow",Triple (fromList [
        (Object {objSig = "Node", identifier = 0},Object {objSig = "Node", identifier = 1},NumberObject {number = 0}),
        (Object {objSig = "Node", identifier = 1},Object {objSig = "Node", identifier = 0},NumberObject {number = 3})
      ("stored",Double (fromList [
        (Object {objSig = "Node", identifier = 0},NumberObject {number = 0}),
        (Object {objSig = "Node", identifier = 1},NumberObject {number = 1})

A retrieval example

Using this library we may retrieve returned signature values using lookupSig, then query parameter variables of the queried predicate using unscoped, and query signature sets and relations using getSingleAs, getDoubleAs, and getTripleAs.

The following Code might for instance be used for the graph example:

newtype Node = Node Int deriving (Eq, Show, Ord)

  :: AlloyInstance
  -> Either String (Set Node, Set (Node, Int), Set (Node, Node, Int), Set (Node), Set (Node))
instanceToNames insta = do
  let node :: String -> Int -> Either String Node
      node = object "Node" Node
  n     <- lookupSig (scoped "this" "Node") insta
  nodes <- getSingleAs "" node n
  store <- getDoubleAs "stored" node int n
  flow  <- getTripleAs "flow" node node int n
  x     <- lookupSig (unscoped "$withFlow_x") insta >>= getSingleAs "" node
  y     <- lookupSig (unscoped "$withFlow_y") insta >>= getSingleAs "" node
  return (nodes, store, flow, x, y)

Calling instanceToNames on the above instance would result in the following expression:

Right (
  fromList [Node 0,Node 1],
  fromList [(Node 0,0),(Node 1,1)],
  fromList [(Node 0,Node 1,0),(Node 1,Node 0,3)],
  fromList [Node 1],
  fromList [Node 0]


Changelog for call-alloy

Unreleased changes

Released changes

  • introduce flag for testing different SAT solvers


  • add support for different SAT solvers

  • fix terminal spamming due to process abortion on Windows

  • make resilient to IO errors due to parallelism or abort

  • fix too early abortion of process execution
  • show raw output on library parsing issues


  • provide required Java libraries in package data directory
  • use async for process interaction
  • terminate calls to Java properly (even on interrupts)

  • fix runtime error on WARN

  • fix runtime error on PARTIAL_INSTANCE

  • support “State0” line in retrieved instances (introduced by Alloy 6)
  • support CRLF at line end


  • upgrade to Alloy 6.0.0
  • allow slashes in object names
  • allow identity relations
  • improve feedback on misspelled/missing relation and signature names
  • remove ‘relToMap’

  • deprecate ‘relToMap’
  • provide functions for returning raw output of instances
  • provide functions for typed retrieval
  • deprecate ‘getSingle’, ‘getDouble’, ‘getTriple’, ‘objectName’

  • fix errors due to long Alloy code by starting timeout after transferring code

  • enable to abort instance generation early by using timeout

  • allow parsing ' as part of words. (Especially skolem may return them if variable names in predicates to check are not unique.)
  • add version constraint for Win32
  • allow later versions of bytestring