1. Specificarea si verificarea sistemelor distribuite
Dorel Lucanu

2. Modele AsmL masini cu stari abstracte stari abstracte
caracterizate de valorile variabilelor
pasi operationali distincti: tranzitii peste stari abstracte
comportarea (executia): secventa de stari conectate prin tranzitii
Dorel Lucanu
SVSD

3. Evolutia variabilelor de stare
Dorel Lucanu
SVSD

4. Exemplu: citirea din fisier
Main()
initially F as File? = null
initially FContents = ""
initially Mode = "Initial"
step until fixpoint
if Mode = "Initial" then
F := new Open("MyFile.txt")
Mode := "Reading"
if Mode = "Reading" and Length(FContents) = 0 then
FContents := Read(F, 1)
if Mode = "Reading" and Length(FContents) = 1 then
FContents := FContents + Read(F, 1)
if Mode = "Reading" and Length(FContents) > 1 then
WriteLine(FContents)
Mode := "Finished"
Dorel Lucanu
SVSD

5. Exemplu: citirea din fisier
Dorel Lucanu
SVSD

6. Procese secventiale step [label] [stopping-condition] statement-block
until fixpoint
until expr
while expr
Dorel Lucanu
SVSD

7. Iteratia de punct fix enum EnumMode Initial Started Finished Main()
initially Mode = Initial
initially Count = 0
step until fixpoint
if Mode = Initial then
Mode := Started
Count := 1
if Mode = Started and Count < 10 then
Count := Count + 1
if Mode = Started and Count >= 10 then
Mode := Finished
Dorel Lucanu
SVSD

8. Iteratia de punct fix Mode = Initial Count = 0 Mode = Started
Mode = Finished
Count = 10
Dorel Lucanu
SVSD

9. Iteratia while Main() initially x = 1 step while x < 10
WriteLine(x)
x := x + 1
Dorel Lucanu
SVSD

10. Iteratia until Main() initially x = 1 step until x > 9 WriteLine(x)
x := x + 1
Dorel Lucanu
SVSD

11. Iteratii peste colectii
step foreach ident1 in expr1, ident2 in expr2 ...
statement-block
exemplu:
const myList = [1, 2, 3]
Main()
step foreach i in myList
WriteLine(i)
Dorel Lucanu
SVSD

12. initially F as File? = null initially FContents = ""
Secventa de pasi
Main()
initially F as File? = null
initially FContents = ""
step 1: F := Open("MyFile.txt")
step 2: FContents := Read(F, 1)
step 3: FContents := FContents + Read(F,1)
step 4: WriteLine(FContents)
Dorel Lucanu
SVSD

13. actualizari var x = 0 // initialize x var y = 1 // initialize y Main()
step
WriteLine ("In the first step, x = " + x)
// x is 0
WriteLine ("In the first step, y = " + y)
// y is 1
x := 2
// update occurs here
WriteLine ("In the second step, x = " + x)
// x is 2
WriteLine ("In the second step, y = " + y)
Dorel Lucanu
SVSD

14. actualizari var x = 0 var y = 1 Main() step
WriteLine ("In the first step, x = " + x)
WriteLine ("In the first step, y = " + y)
x := 2
WriteLine ("In the second step, x = " + x)
// x is still 0
Dorel Lucanu
SVSD

15. Interschimbarea de valori
var x = 1
var y = 2
Main()
step
x := y
y := x
// updates not yet taken effect
WriteLine ("In the first step, x = " + x)
WriteLine ("In the first step, y = " + y)
// updates have taken effect
WriteLine ("In the second step, x = " + x)
WriteLine ("In the second step, y = " + y)
Dorel Lucanu
SVSD

16. Actualizarea de multimi
var Students as Set of String = {}
Main()
step
WriteLine ("The initial roster is = " +
Students)
Students := {"Bill", "Carla", "Duncan",
"Amy"}
WriteLine ("The final roster is " +
Dorel Lucanu
SVSD

17. Actualizarea de multimi
var Students as Set of String = {}
Main()
step
WriteLine ("The initial roster is = " +
Students)
add "Bill" to Students
add "Carla" to Students
add "Duncan" to Students
add "Amy" to Students
WriteLine ("The final roster is " +
Dorel Lucanu
SVSD

18. IsWord(i as Integer) as Boolean return (0 <= i and i <= 0xFFFF)
Metode
name( parameter_1 as Type, ...parameter_n as Type ) as Type
name este numele metodei
( parameter_1 as Type, ...parameter_n as Type ) este lista valorilor trimise metodei
as Type este tipul valorii returnate de metoda (in cazul in care exista)
IsWord(i as Integer) as Boolean
return (0 <= i and i <= 0xFFFF)
Main()
step
if IsWord(123) then
WriteLine("123 is a word of memory.")
Dorel Lucanu
SVSD

19. Increment() // update procedure Count := Count + 1
Metode
var Count = 0
Increment() // update procedure
Count := Count + 1
CurrentCount() as Integer // function
return Count
Main()
step
Increment()
WriteLine("x is " + CurrentCount())
Dorel Lucanu
SVSD

20. Variabile locale Main() step mySet1 = {1, 2, 3}
WriteLine("mySet1 has " +
Size(mySet1) +
" elements.")
mySet2 = mySet1 union {4}
WriteLine("mySet2 has " +
Size(mySet2) +
Dorel Lucanu
SVSD

21. Supraincarcarea metodelor
Max(i as Integer, j as Integer) as Integer
return (if i > j then i else j)
Max(s as Set of Integer) as Integer
return (any m | m in S where
not (exists n in S where n > m))
Main()
step WriteLine("The largest number in the set is “
+ Max(S))
step WriteLine("The larger of the two integers is “
+ Max(2, 3))
Dorel Lucanu
SVSD

22. Location(1, 4) este o valoare a structurii Location
structure Location
base as Integer
offset as Integer
Location(1, 4) este o valoare a structurii Location
Dorel Lucanu
SVSD

23. IsTicketID(i as Integer) as Boolean require i > 0
Asertiuni
AllTickets = { }
IsTicketID(i as Integer) as Boolean
require i > 0
return (i in AllTickets)
ChooseAnyTicket() as Integer
ensure IsTicketID(result)
return (any t | t in AllTickets)
Dorel Lucanu
SVSD

24. Constante si variabile
x as Integer = 10 // constanta globala
// cu tip explicit
x = // constanta globala
// cu tip implicit
variabile:
var x as Integer = 10
var x = 10
var greeting as String = "Hello"
var y = [1..6]
var menu = {"ham", "cheese", "blt"}
Dorel Lucanu
SVSD

25. var p1 = new Person("William", 40) var p2 = new Person("Amy", 20)
Clase
class Person
var name as String
var age as Integer
var p1 = new Person("William", 40)
var p2 = new Person("Amy", 20)
Main()
step
p1.name := "Bill"
WriteLine("Name of p1 is " + p1.name)
WriteLine("Name of p2 is " + p2.name)
Dorel Lucanu
SVSD

26. RenamePerson(p as Person, newName as String) p.name := newName Main()
Instante ca referinte
class Person
var name as String
var age as Integer
RenamePerson(p as Person, newName as String)
p.name := newName
Main()
var p1 = new Person("William", 40)
step
RenamePerson(p1, "Bill")
WriteLine("Name of p1 is " + p1.name)
Dorel Lucanu
SVSD

27. var Bob = new Person(30, "Jones") var Amy = new Person (20, "Smith")
Clase ca referinte
class Person
var age as Integer
var LastName as String
Main()
var Bob = new Person(30, "Jones")
var Amy = new Person (20, "Smith")
var BobsFriend = Amy
step
BobsFriend.age := 21
WriteLine("Amy's age is " + Amy.age)
Dorel Lucanu
SVSD

28. return(length * width * height) class FragileBox extends BasicBox
Clase derivate
class BasicBox
var length as Double
var width as Double
var height as Double
Volume() as Double
return(length * width * height)
class FragileBox extends BasicBox
return(0.85 * length * width * height)
Dorel Lucanu
SVSD

29. Structuri alternative
structure InputEvent
case KeyInput
key as Char
case SwitcherInput
toggle as Boolean
case CoinInput
coin as Integer
case CoinReturn
// no data needed
HandleInput(e as InputEvent)
match e
KeyInput(k): WriteLine("Key was pressed: " + k)
SwitcherInput(t): WriteLine("Switch flipped: " + t)
CoinInput(c): WriteLine("Coin inserted: " + c)
CoinReturn(): WriteLine("Coin return pressed.")
Dorel Lucanu
SVSD

30. C = {(i, j) | i in A where i < 4, j in A where j < i}
Multimi
A = {1..5}
C = {(i, j) | i in A where i < 4, j in A where j < i}
Main()
step
WriteLine (C)
Dorel Lucanu
SVSD

31. Evaluare paralela class Person var age as Integer Amy = new Person(20)
Bob = new Person(16)
Duncan = new Person(40)
People = {Amy, Bob, Duncan}
GrowOlder()
forall p in People
p.age := p.age + 1
var year = 2000
Main()
step while year < 2010
WriteLine("Amy's age is " + Amy.age + " in " + year)
WriteLine("Bob's age is " + Bob.age + " in " + year)
WriteLine("Duncan's age is " + Duncan.age + " in " + year)
year := year + 1
Dorel Lucanu
SVSD

32. Evaluare paralela
Dorel Lucanu
SVSD

33. Iteratie secventiala peste o colectie
class Person
var age as Integer
var Amy = new Person (20)
var Bob = new Person (16)
var Duncan = new Person (40)
People = {Amy, Bob, Duncan}
GrowOlder()
step foreach p in People
p.age := p.age + 1
var year = 2000
Main()
step while year < 2010
WriteLine("Amy's age is " + Amy.age + " in " + year)
WriteLine("Bob's age is " + Bob.age + " in " + year)
WriteLine("Duncan's age is " + Duncan.age + " in " + year)
year := year + 1
Dorel Lucanu
SVSD

34. Iteratie secventiala peste o colectie
Dorel Lucanu
SVSD