Programming with Scala: Language Exploration

205 Pages·2017·1.439 MB·

by  Bhim P. Upadhyaya (auth.)

Undergraduate Topics in Computer Science
Bhim P. Upadhyaya
Programming
with Scala
Language Exploration
Undergraduate Topics in Computer Science
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Ian Mackie
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Andrew Pitts, University of Cambridge, Cambridge, UK
Hanne Riis Nielson, Technical University of Denmark, Kongens Lyngby, Denmark
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Iain Stewart, University of Durham, Durham, UK
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Bhim P. Upadhyaya
Programming with Scala
Language Exploration
Bhim P. Upadhyaya
Carnegie Mellon University – Silicon Valley
NASA Ames Research Park
Bldg. 23, Moffett Field
CA 94035
USA
ISSN 1863-7310 ISSN 2197-1781 (electronic)
Undergraduate Topics in Computer Science
ISBN 978-3-319-69367-5 ISBN 978-3-319-69368-2 (eBook)
https://doi.org/10.1007/978-3-319-69368-2
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-Bhim
Preface
We are living in a very interesting time, in terms of technological advancements
among other things. In the last 60 years, humanity has made tremendous progress
in the field of computing. High level programming languages appeared in the late
1950s,buttherewerenomicroprocessorsavailable.Onecanimaginehowtedious
it could be to program. With the invention of microprocessors in the late 1960s,
thisfieldgotagreatboost.Alongwithhardwaredevelopments,newhighlevelpro-
gramminglanguagesstartedemerging.AmongthosearePascal,Smalltalk,C,etc.
Some of these languages are still widely used. One of the interesting facts about
thesehighlevellanguagesisthattheyhadnicheapplicationareas,eventhoughthey
werewidelyprojectedasgeneralpurposelanguages,includinginthetextbooks.For
example,Pascalwasleaningtowardeducation,Cwasprimarilydevelopedtoease
operating systems developments, Fortran was for scientific computing, etc. What-
everthedomains,eachoftheselanguageshasshapedthehistoryofcomputing.
Today,shapes,sizes,andcapacitiesofcomputingdevicesaremuchdifferentthan
60yearsago.Inthelast20years,computinghasshiftedfromlocalizedclient-server
environmentstoworldwideclient-serverenvironments.Thereareseveralcatalysts
for this change, including the invention of the world wide web, the advancements
inintegratedcircuits,andtheinnovationsindevicemanufacturing.Oneofthecat-
alysts, which doesn’t get enough credit, is the advancements of programming lan-
guages.Developersaretrulyenabledbylanguageinnovations.Theinnovationthat
JVM brought, has greatly impacted software engineering in general, and Internet
basedapplicationsdevelopmentinparticular.Beingabletoprogram,withoutwor-
rying about incompatibilities with hundreds of vendor specific architectures, is a
greatreliefforsoftwareengineers.
Oneoftheimportantaspectsofadvancements,notdiscussedenough,inindus-
trial settings is knowledge evolution. I have had the privilege of working for the
world’slargest(non-profit)organization,theUnitedNations,whichgavemeanop-
portunitytoworkwithpeoplefromalmosteverymajorculturalbackground.AlsoI
haveworkedforsomeofthelargestandfinestfor-profitorganizationsintheworld.
Inadditiontothis,Iwasfortunateenoughtobepartofsomeofthefinestuniversities
in the world, either through academic programs, or by working directly with aca-
vii
viii Preface
demicians in unique settings. This experience allows me to make some inferences
on knowledge evolution, specially in the field of software engineering. The first
inference is that changing a programming language is not pleasant, specially for
professional programmers. The second inference is that adapting a new language
to the level that one can sell the skills has strong limitations. The third inference
is that the popularity of a particular language is strongly affected by the industry–
academicloop,directlyorindirectly.Tobeprecise,howalanguageistaught,where
itistaught,whatkindoflearningmaterialsareavailable,etc.,determinehowpopu-
laralanguagewillbecome.
Dr.MartinOdersky,thecreatorofScala,hasdoneagreatjobofalanguageinno-
vation.Scalanotonlyprovidesanopportunitytoprograminmultipleparadigms,but
alsomakesdevelopersmoreproductivewithtoday’scomputinginfrastructure.Most
oftheearlierlanguageswerenotdesignedtoprogramindistributedenvironments.
Also most of them were not designed to evolve. One of the fascinating aspects of
Scalaisthatitcanbegrown,basedondevelopers’needs.Remember,foreveryge-
nius,thereisalimittohowmanylanguagesonecanbecomeexpertin.Itispretty
muchlikethecaseofnaturallanguages.Wecanrecallourselves,howgoodweare
inourmothertongueandhowgoodweareinotherlanguages.Dowestruggle?The
Scalacreatorhasgiftedabeautifulsolutiontotheworldofcomputerprogrammers.
With this book, I have tried to enrich the learning aspect of Scala. I strongly
believe that Scala can be a great first programming language. There is no need to
leanonanyotherprogramminglanguageinordertolearnit,excepttheenvironment,
which is JVM for a good reason. The approach that I have taken in this book was
primarilyinspiredbymyfirsthandobservationsofhowprofessionalprogrammers
masteranewtechnology.Alsoitispartlyinfluencedbymyexperienceofteaching
undergraduatecomputerscienceandengineeringstudents,overhalfadecade.Ihave
tried to present complete and runnable programs, whenever possible. In the last
12 years, I noticed professional programmers learning faster by tweaking existing
programs.Thiswastrueformyundergraduatestudentsaswell.Tweakingallowed
learners to build self-confidence, which I found was the basis for the majority of
learnersfortheirlongtermpursuits.Thisbookcanbeused,bothatanundergraduate
levelandatagraduatelevel,toteachafirstprogrammingcourse.Alsoitisagreat
companionforprofessionalprogrammersplanningtoswitchtoScala.
Each chapter has review questions to reinforce your learning, which makes
youreadyforproblemsolving.Youwillfindyourselfadequateandself-confident,
therebykeepingyouawayfromthepathoffrustration.Ihaveseenmanygreatpro-
fessional programmers being frustrated while learning a new language. Also each
chapter has problems to solve. These problems are much closer to what you will
need when you embark on your career as a professional Scala programmer. The
process of solving problems expands your knowledge boundary; you are moving
fromreinforcingtodevelopingsalableskills.
Sunnyvale,California BhimP.Upadhyaya
June2017
Contents
1 IntroductiontoComputing...................................... 1
1.1 IntroductiontoComputers ................................... 3
1.1.1 BasicComponents ................................... 3
1.1.2 Operation........................................... 4
1.2 OperatingSystems ......................................... 5
1.3 ProgrammingLanguages .................................... 6
1.4 IntroductiontoScala........................................ 9
1.5 ProgramAttributes ......................................... 12
1.6 Conclusion................................................ 13
1.7 ReviewQuestions .......................................... 14
1.8 Problems ................................................. 14
1.9 AnswerstoReviewQuestions ................................ 15
1.10 SolutionstoProblems....................................... 16
2 ScalaFundamentals ............................................ 17
2.1 Literals ................................................... 17
2.1.1 CharacterLiterals.................................... 17
2.1.2 StringLiterals....................................... 18
2.1.3 IntegerLiterals ...................................... 19
2.1.4 FloatingPointLiterals ................................ 19
2.1.5 BooleanLiterals ..................................... 20
2.1.6 EscapeSequences.................................... 20
2.1.7 SymbolLiterals ..................................... 21
2.1.8 OtherLexicalElements ............................... 21
2.2 IdentifiersandReservedWords ............................... 23
2.3 Types .................................................... 23
2.4 DeclarationsandDefinitions ................................. 24
2.5 Expressions ............................................... 26
2.6 Conclusion................................................ 28
2.7 ReviewQuestions .......................................... 28
2.8 Problems ................................................. 28
ix
x Contents
2.9 AnswerstoReviewQuestions ................................ 29
2.10 SolutionstoProblems....................................... 29
3 ClassesandObjects ............................................ 31
3.1 ClassMembers ............................................ 31
3.2 ClassDefinitions ........................................... 33
3.3 ObjectDefinitions .......................................... 33
3.4 Conclusion................................................ 34
3.5 ReviewQuestions .......................................... 34
3.6 Problems ................................................. 34
3.7 AnswerstoReviewQuestions ................................ 34
3.8 SolutionstoProblems....................................... 35
4 ControlStructures ............................................. 37
4.1 ConditionalExpressions..................................... 37
4.2 ForExpressions............................................ 39
4.3 WhileLoops............................................... 42
4.4 ExceptionHandling......................................... 43
4.5 Conclusion................................................ 45
4.6 ReviewQuestions .......................................... 45
4.7 Problems ................................................. 46
4.8 AnswerstoReviewQuestions ................................ 46
4.9 SolutionstoProblems....................................... 47
5 Operators ..................................................... 51
5.1 OperatorsasMethods ....................................... 51
5.2 ArithmeticOperators ....................................... 52
5.3 RelationalandLogicalOperators ............................. 54
5.4 BitwiseOperators .......................................... 55
5.5 OperatorPrecedenceandAssociativity......................... 56
5.6 Conclusion................................................ 57
5.7 ReviewQuestions .......................................... 58
5.8 Problems ................................................. 58
5.9 AnswerstoReviewQuestions ................................ 58
5.10 SolutionstoProblems....................................... 59
6 DataInputandOutput ......................................... 63
6.1 RegularExpressions ........................................ 63
6.2 SingleCharacterInput ...................................... 66
6.3 SingleCharacterOutput ..................................... 67
6.4 ReadingFromaFile ........................................ 68
6.5 WritingtoaFile ........................................... 69
6.6 NavigatingDirectories ...................................... 70
6.7 Conclusion................................................ 72
6.8 ReviewQuestions .......................................... 72
6.9 Problems ................................................. 72