CSE-321 Programming Languages

Overview

POSTECH

March 5, 2007

박성우

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Neanderthal Man

OneTwoThree???

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Why are two left???Foolish Neanderthal!I can count up to ten!

Java Man

I got five.I've eaten three.

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Language = Frame of Thought• The language defines the frame of thought.

– what you can communicate to others– what concepts you are able to think over– how you think

• Big question:

"Does the programming language define the frame of thought in the course of programming?"

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C Exercise: Integration• Specification

– input: function f from int to int range a and b

– output: f(a) + f(a + 1) + ... + f(b)

• Solution?int integral(int (*f)(int), int a, int b) {

int i, sum = 0;for (i = a; i <= b; i++)

sum += f(i);return sum;

}

• Question: what if there were no function pointer?

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C Exercise: Derivative• Specification

– input: function f from float to float– output: derivative f' of f such that

f'(x) = (f(x + ) - f(x)) /

• Solution?

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Question for You• What is your favorite language?

– Assembly, Basic, Pascal, C, C++, C#, Java, Perl, Python, Ruby, Prolog, Lisp, SML, Haskell, ...

• What is its strength?• What is its weakness?• What is its limitation?

• Do you think your language defines the frame of thought?

Maybe we can find the answer by learning new programming

languages.

Here is my story.

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BASIC• 1984• Disappointing ;-(

– It does not compile to machine code.– It is slow.– “So I cannot make a computer game!”

• Had to learn anyway:– to run computer games stored in cassette tapes

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C• 1991• Exciting ;-)

– It compiles to machine code.– “So maybe I can make a computer game!”

• “Return of the Jedi” (1983) and DOOM (1993)

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C++• 1993• Cool!

– object-orientation (whatever that means)– instantly appreciated its power.

• Remark by the instructor:

“C++ will become the most dominant programming language in a decade from now.”

– Is it?

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Java• 1995• Incredible!

– Not only object-orientation but also garbage collection!• no more hassle of memory allocation and

deallocation– Virtual Machine lets you run the code

“everywhere.”– The syntax and semantics seemed flawless.

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Anyone recognizes this picture?

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Familiar?

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WTH?

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ML• 1995• Eye-opener!

– functional language– strong type system

• ML = “Meta-Language”• Lessons that I learned:

– Programming is not about coding.– Programming is about design and specification.

But this course is not about learning new programming languages;

it is about programming language theory.

Then why do we study programming language theory?

) Because there is an ever growing need for new programming languages!

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Mars Climate Orbiter Failure in 1998

• Destroyed due to a navigation error• Cause?

– One module used English units (feet).– The other module expected metric units (meter).

• Stupidity:– NASA scientists? No!– programming languages they used? Yes!

• Cf. Fortress at SUN Microsystems– support for dimension analysis

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Common Features???

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... runs faster on

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Multi-core CPUs• IBM Power4, dual-core, 2000• Intel reaches thermal wall, 2004 ) no more free lunch!• Intel Xeon, quad-core, 2006• Sony PlayStation 3 Cell, eight cores enabled, 2006

• Intel, 80-cores, 2011 (prototype finished)

source: Herb Sutter - "Software and the concurrency revolution"

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Tim Sweeney's POPL '06 Invited Talk- Last Slide

Programming Language People

Course Overview

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Topics to Be Covered• Inductive reasoning• -Calculus• Type theory• Object-orientation• Concurrency

• Note:– This course is not about functional languages.– It is about basic programming language theory.

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Grading• 50% assignments

– 8 programming assignments, all in Standard ML• 10% quizzes

– 4 quizzes (substitute for written assignments)• 20% midterm, • 20% final

• Why 50% for quizzes and exams?– average of 2006 midterm: 53.66 of 100– average of 2006 final: 27.62 of 80

• Closed book for quizzes and exams

• Absolute grading system in 2007vs. Relative grading system in 2006

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NO CHEATING• Read the document on the disciplinary policy.

• 2006– 7 students cheated (out of 46 students)– 2 suspicious cases

• Cheating will not be tolerated.– Cheating even once will expel you from class or get

you an F.– We will check your programs at the end of the semester.

• You should complete your assignments on your own.

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Homework by Wednesday• Visit the course webpage.

– http://www.postech.ac.kr/~gla/cs321/• Visit the discussion board.

– telnet pl.postech.ac.kr• Install

– Standard ML 110.58.– AFS client software.

• Read "A Critical Look at Programming Languages".