Listoflectures
IntroductionandFunctionalProgramming
ImperativeProgrammingandDataStructures
3
Environment
4
Evaluation
5
ObjectOrientedProgramming
6
Macrosand
7
VirtualMachinesandBytecode
8
GarbageCollectionandNativeCode
9
DistributedComputing
10
Logic
11
Guestlecture
12
Summary
1
TDDA69DataandProgramStructure
ImperativeProgramming
andDataStructures
CyrilleBerger
2
2/51
Lecturegoal
Lecturecontent
Introducewhatisimperative
programming,advantagesand
inconvenient
Introducedatastructuresandhow
theycanbeusedinthedifferent
programmingparadigms
ImperativeProgramming
Statements
ConditionalStatement
IterativeStatements
Advantages/Incovenients
Data
ArrayandList
Tree
TreeWalking
TreeRecursion
Dictionnary
3/51
4/51
Whatisimperativeprogramming?
Expresshowcomputationare
executed
Describescomputationintermofstatements
thatchangetheinternalstate
Verysimilartorecipes
ImperativeProgramming
Examples:C/C++,Pascal,
Java,Python,JavaScript...
6
Foundationsofimperativeprogramming
MosthardwarefollowtheVonNeumannarchitecture,whichisimperative
CentralProcessingUnit
Inputdevice
ControlUnit
Arithmetic/LogicUnit
Statements
Outputdevice
MemoryUnit
Manyoftheearlyimperativeprogramminglanguages(Fortran,C...)are
abstractionsofassemblylanguage
ExampleofnonVonNeumann:FPGA(reconfigurablecomputer
architecture)
7
Statements
Expressionstatements
Astatementisexecutedbythe
interpretertoperformanaction
Sameexpressionsasinfunctional
programming
2
plus
'hello'
Statement
<header>:
<statement>
<statement>
...
<statement>
<optionalseparatingheader>:
<statement>
<statement>
...
<statement>
...
Suite
Clause
max
(
2
,
Compoundexpressions
3
)
max(min(pow(3,5),-4),min(1,-2)*2)+6
9
10
Assignmentexpression
Assignmentexpression
a=2;a:=2;a<-2;(seta2)...
Global
ConditionalStatement
11
if/else
ConditionalStatement
Astatementthatperformdifferent
computationsdependingona
booleanexpression
InPython:
defabs_val(x):
if(x<0):
return-x
elif(x==0):
return0
else
returnx
InECMAScript/JavaScript:
functionabs_val(x)
{
if(x<0)
{
return-x;
}elseif(x===0)
{
return0;
}else{
returnx;
}
}
Howmanystatementsintheabs_valfunction,
inPython?InECMAScript?
www.govote.at662931
13
Whatdoesthisprogramoutput?
x=2
y=4
ifx==y2:
print("a")
else:
print("b")
ifx:
print("c")
else:
print("d")
ifx-2:
print("e")
else:
print("f")
14
ImperativeconditionvsFunctionalcondition
Imperative:
functionabs_val(x)
{
varresult;
if(x<0)
{
result=-x;
}elseif(x===
0)
{
result=0;
}else{
result=x;
}
returnresult;
}
www.govote.at285968
15
Functional:
functionabs_val(x)
{
returncond(x<0,
-x,
cond(x===
0,
0,
x);
}
16
Booleanexpressions
switch
InPython:
Conditionalswitchbasedonthevalueofan
switch(a)
{
case0:
dosomething;
break;
case'hello'
dosomethingelse;
break;
caseTrue:
dosomeother
thing;
break;
}
Thisisnotjustsyntaxic
Falsevalues:False,0,'',None,0.0,[],{},()
Truevalues:anythingelse(True,1,2,'hello'...
itgivesperformanceadvantage
17
18
Whileloop
IterativeStatements
Allowstatementstobeexecuted
repeatedlyaslongasa
conditionhold
i,total=0
whilei<3:
i=i+1
total=total+i
20
Forloop
Breakstatements
Exitthecurrentloop
Convenientstatementforloopingon
ranges
i,total=0
whileTrue:
i=i+1
total=total+i
ifi<3:
break;
InJavaScript/ECMAScript:
vartotal=0;
for(vari=0;i<3;++i)
{
total=total+i;
}
InPython:
total=0
foriinrange(0,3):
total=total+i
21
22
ImperativeProgramming'sstrength
Naturalwayofexpressingprograms:
Advantages/Incovenients
Closetothe
Programsarewrittenasalistof
Moreefficientthanfunctional
Popular
Statesareuseful
Simulations
Howdoyouimplementafunctional
randomnumbers?
24
Inconvenients
StatesinducesideUnexpectedbehavior
Datarace
Datastructures
25
Array
ArrayandList
Collectionofelements,identified
byanindex
Indexusuallystartsat0
untillength-1
Arraysallowrandom
vararray=[1,4,8]
console.log(array[0].array[1],array[2]);
28
List
ListOperations
A(linked-)listisasequenceof
valueswhereeachentry
containsapointertothenext
1
element
4
8
Operationsonlist
Constructorforcreatinganemptylistnew_list
Testifalistisemptyis_empty
Prependanelementtothelistprepend
Appendanelementtothelistappend
Returnthefirstelementhead
Returnalltheelementsexceptthefirsttail
ø
29
ExampleofListImplementation(1/3)
30
ExampleofListImplementation(2/3)
Eachelementisatwoelements
array
Eachelementisatwoelementsarray
varlist=[1,[4,[8,null]]]
Prependanelement:
functionprepend(arr,val){
if(is_empty(arr))return[val,null];
return[val,arr];
}
Thefirstelementisthe
ThesecondisthenextelementoranullExample:varlist=[1,[4,[8,null]]
Appendanelement:
functionappend(arr,val){
if(is_empty(arr))return[val,null];
varptr=arr;
while(ptr[1]!=null)
{
ptr=ptr[1]
}
ptr[1]=[val,null]
returnarr;
}
Constructor:
functionnew_list(){return[]
Emptytest:
functionis_empty(arr){returnarr.length
===0;}
31
Suggestasolutionto
improvetheappendfunction
www.govote.at9943
32
ExampleofListImplementation(3/3)
Arrayvslist
Eachelementisatwoelementsarray
Arrays:random-access,efficient
unlessyouneedtoresize
Lists:accessthroughiteration,
o(1)forinsertion
PurelyFunctionalRandom-Access
Lists,ChrisOkasaki,InFunctional
ProgrammingLanguagesand
ComputerArchitecture
varlist=[1,[4,[8,null]]]
Returnthefirst
functionhead(arr){
returnarr[0];
}
Returnalltheelementsexceptthe
functiontail(arr){
returnarr[1];
}
33
34
Tuple
Iterating
orderedlistofelements
InPython:
Usingthearrayindex:
Usingthearrayindex:
Usingforeach:
Usingforeach:
functionprint_arr(arr)
{
for(vari=0;i<arr.length;+
+i)
{
console.log(arr[i])
}
}
Notmutablelist
Convenientforfunctionreturn:
defmake_tuple(a,b,c):
return(a,b,c)
(a,b,c)=make_tuple(1,2,3)
functionprint_arr(arr)
{
for(varvalofarr)
{
console.log(val)
}
}
35
defprint_arr(arr):
i=0
while(i<size(arr)):
print(arr[i])
defprint_arr(arr):
for(valinarr):
print(val)
36
Range
Arangeisasequenceof
range(startingvalue,
endingvalue)
Tree
range(-2,2)->[-2,-1,0,1]
Usefulinforloop
foridxinrange(0,arr.length):
print(arr[idx])
37
Tree
ExampleofTreeImplementation
Atreeiseitherasinglevalue
calledaleaforasequence
oftrees
1
2
4
ø
8
Usinganarray
Thefirstelementisthevalue
Thesecondisalistofchildren
Example:
[1,[[2,[]],[4,[[8,[]]]]]]
defcreate_tree(val,*children):
return[val,list(children)]
create_tree(1,createTree(2),createTree(4,
createTree(8)))
ø
39
40
Listener
Atreelistenerisatypeoftreewalkingwhere
afunctioniscalledwhenenteringanode
andwhenexitingit
TreeWalking
deftree_listener(tree,entering,exiting):
entering(tree)
forcintree[1]:
tree_listener(c,entering,exiting)
exiting(tree)
defprint_node(tree):
print(tree[0])
tree_listener([1,[[2,[]],[4,[[8,[]]]]]],print_node,
>>12248841
42
Visitor
Atreevisitorisatypeoftreewalkingthenodes
intreearevisitedrecursively
deftree_visitor(tree):
if(len(tree[1])==0):
return1
val=1
forcintree[1]:
val=max(val,
tree_visitor(c))
returnval+1
tree_visitor([1,[[2,[]],[4,[[8,[]]]]]])>>?
www.govote.at192598
TreeRecursion
HowwellwouldthatworkinPythonforinfinitely
deeptrees?
Why?www.govote.at629459
43
TreeRecursion
ATree-RecursiveProcess
Thecomputationalprocessoffib
evolvesintoatreestructure
Tree-shapedprocessesarisewhenever
executingthebodyofarecursivefunction
makesmore
n:0,1,2,3,4,5,6,7,8,...,35
fib(n):0,1,1,2,3,5,8,13,21,...,9227465
fib(5)
deffib(n):
ifn==0:
return0
elifn==1:
return1
else:
returnfib(n-2)+
fib(4)
fib(3)
fib(3)
fib(2)
fib(1)
fib(2)
fib(1)
fib(1)
fib(2)
fib(0) fib(1)
fib(1)
fib(0)
fib(0)
45
46
Memoization
RepetitionnTree-RecursiveComputation
Thisprocessishighlyrepetitive;fibis
calledonthesameargumentmultiple
fib(5)
times.
fib(4)
fib(3)
fib(3)
fib(2)
fib(1)
fib(2)
fib(1)
Memoization:storeresultsofexpensivefunction
calls
fib(1)
fib(2)
fib(0) fib(1)
fib(1)
fib(0)
__fib_cache={0:0,1:1}
deffib_cached(n):
ifnin__fib_cache:
return__fib_cache[n]
else:
__fib_cache[n]=fib_cached(n-2)
+
fib_cached(n-1)
return__fib_cache[n]
Timing:
fib(0)
fib(9000)->>24h
fib_cached(9000)->8.77ms(arrayversion
fib_fast_doubling(9000)->6.1ms
Howwouldyouimprove?
www.govote.at689
47
48
Dictionnary
Adictionnaryisanassociativearray,where
eachelementisassociatedtoanindex
Typeofindex,anythingthatcanbeordered(with
<)orcomparedandandevenbetterifahashcan
becomputed
Dictionnary
Integer,notnecesseralycontinuous
Strings
Example:
varmap={1:0,'hello':'world'}
console.log(map[1],map['hello'])
Inmanydynamicobjectoriented
programminglanguages,Objectsare
Disctionnaries:Python,JavaScript/
ECMAScript...
Summary
Imperativeprogramming
Data
51/51
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