1. Welcome to Programming Languages!

2. Why take Programming Languages?
Make me a better ________________

3. Why take Programming Languages?
Make be a better creator of PLs
Design PLs
Implement PLs
Make me a better user of PLs
Write better code
Choose right PL for job

4. Deep questions What makes a good PL design?
What types of PL designs are there?
How do you implement a PL?

5. Can you guess what this is?
It’s a program!
Machine language – x86 (Pentium)
Expressed as hex
Calculates greatest common divisor (GCD)
It’s a program!
It calculates the greatest common divisor (GCD) of two integers.
Can you guess what language?
It’s machine language (expressed as hex) for the x86 (Pentium) instruction set.

6. What are the pros/cons of machine language?
Close to machine
Performance
Unreadable
Not portable
More???

7. Can you guess what this is?
Assembly language version of GCD program
1-to-1 mnemonic mapping to machine language

8. What are the pros/cons of assembly language?
Pretty much same as machine language, but more human readable

9. Can you guess what this is?
High-level language (C/C++) version of GCD

10. What are the pros/cons of high-level language?
Pros: More comprehendible, scalable, and portable
Cons: Farther from the machine (poorer performance)

11. But there are thousands(
But there are thousands(?) of high-level langs – what makes one better than another?
C/C++
Scheme/Lisp
Prolog

12. What makes one lang better than another?
Expressive power
What computations can you express?
Usability
Learnability
Ease of use (create/read/modify)
Ease of implementation
Performance
Tool support
Familiarity/expertise???

13. Deep questions What makes a good PL design?
What types of PL designs are there?
How do you implement a PL?

14. Declarative versus Imperative
Say what to compute
Programmers point of view
Higher level
Up and coming
Say how to compute
Implementers point of view
Closer to machine
Dominant

15. (Fuzzy) Categories of languages
Declarative
functional (Lisp/Scheme, ML, Haskell)
dataflow (Id, Val)
logic, constraint-based (Prolog, spreadsheets)
template-based (XSLT)
Imperative
von Neumann (C, Ada, Fortran, …)
scripting (Perl, Python, PHP, …)
object-oriented (Smalltalk, Eiffel, Java, …)

16. Functional versus von Neuman
Functional - Scheme/Lisp
Recursive definition of functions, refining from more complex to simpler (no variables/state!)
von Neumann - C/C++
Declaration and sequential modification of variables

17. Deep questions What makes a good PL design?
What types of PL designs are there?
How do you implement a PL?

18. Finish this dataflow diagram for assembly language
???

19. Finish this dataflow diagram for assembly language

20. Finish this dataflow diagram for high-level languages
???

21. Finish this dataflow diagram for high-level languages
Don’t let the names confuse you. These are all translators

22. Architectural pattern
Architectural pattern*: Translate through many intermediate representations
* Called pipeline or pipes and filters architecture

23. But there’s another way!
Can you explain this diagram?

24. Translators Versus Interpreters
Translator: Program that reads “sentences” in one language and converts them to another
See also compilers, assemblers
Interpreter: Program that reads sentences in some language and “executes” them
May or may not be interactive

25. What language uses this translator/interpreter hybrid architecture?
aka Compiler
aka Interpreter
Why, Java, of course

26. How do you read/analyze/process code?…
What happens in here?

27. Two big concerns Syntax: The form in which sentences are expressed
What syntactic elements do parts of the source map to?
Is the source syntactically valid?
Semantics: The meaning of the sentences
What semantic elements do parts of the source map to?
Is the source semantically valid?

28. What to do first?

29. Split input into bite-size tokens
C/C++ token examples:
What next?

30. Map tokens to syntactic elements
C/C++ parse tree example:
What next?

31. Represent program in terms of semantic elements
AST example
What next?

32. And all the rest…
And all the rest…

33. Fortunately, there are tools to help you!
Compiler Compilers
aka Compiler Generators
aka Parser Generators
aka…
Examples:
Lex/Yacc
Flex/Bison
ANTLR

34. Course Goals
Learn to create your own language translators/interpreters
Using ANTLR
Survey issues and features in PL design
Try programming in sampling of different languages

35. Course Structure Three parts (4-5 weeks each)
Follows structure of PLP book
Each ends in an exam
Homeworks throughout (~7)
Readings + quizzes throughout

36. Grading 51% exams (3 x 17%) 39% homeworks and quizzes
10% participation

37. Some key policies No cheating!
I use plagiarism detection system!
Participate! (lest you lose a participation point)
Be here at beginning of class, stay until the end
Pop quizzes at beginning of class common
Be engaged!
Expect seating chart
Bring laptops, but…

39. Let’s tour the course web pages…

40. What’s next? Take Java proficiency instrument Do Homework 0
In class today
Do Homework 0
Due Tuesday by 2:40