1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
|
-----------------------------------------------------------------------------
-- |
-- Module : Documentation.SBV.Examples.Queries.Enums
-- Copyright : (c) Levent Erkok
-- License : BSD3
-- Maintainer: erkokl@gmail.com
-- Stability : experimental
--
-- Demonstrates the use of enumeration values during queries.
-----------------------------------------------------------------------------
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE TemplateHaskell #-}
{-# OPTIONS_GHC -Wall -Werror #-}
module Documentation.SBV.Examples.Queries.Enums where
import Data.SBV
import Data.SBV.Control
-- | Days of the week. We make it symbolic using the 'mkSymbolicEnumeration' splice.
data Day = Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday
-- | Make 'Day' a symbolic value.
mkSymbolicEnumeration ''Day
-- | A trivial query to find three consecutive days that's all before 'Thursday'. The point
-- here is that we can perform queries on such enumerated values and use 'getValue' on them
-- and return their values from queries just like any other value. We have:
--
-- >>> findDays
-- [Monday,Tuesday,Wednesday]
findDays :: IO [Day]
findDays = runSMT $ do (d1 :: SDay) <- free "d1"
(d2 :: SDay) <- free "d2"
(d3 :: SDay) <- free "d3"
-- Assert that they are ordered
constrain $ d1 .<= d2
constrain $ d2 .<= d3
-- Assert that last day is before 'Thursday'
constrain $ d3 .< sThursday
-- Constraints can be given before or after
-- the query mode starts. We will assert that
-- they are different after we start interacting
-- with the solver. Note that we can query the
-- values based on other values obtained too,
-- if we want to guide the search.
query $ do constrain $ distinct [d1, d2, d3]
cs <- checkSat
case cs of
Sat -> do a <- getValue d1
b <- getValue d2
c <- getValue d3
return [a, b, c]
_ -> error "Impossible, can't find days!"
|
