Thursday, January 20, 2005

SICP - Overview and Introduction to LISP ( lecture 1B)

Well this lecture was pretty interesting.

Initally the professor spoke about the substitution model.

Two very interesting programs for addition of 2 numbers were introduced. Using these programs the concepts of Iterative and Recursive processes were introduced. Was very interesting.

Iterative Process - X
Time Complexity - O(X)
Space Complexity - O(1)

Recursive Process - X
Time Complexity - O(X)
Space Complexity - O(X)
Where X is some parameter that is used in the computation process.

Fibonacci series were introduced.

The last part was on the problem of "The towers of Hanoi". Long time since i have seen this problem. I had seen this last in my third semester of Engineering. We had hurridly hacked together a C programm in a C++ environment and subject :-)) .. Anyways it was interesting how the concept of recursion was introduced here. There were props and the code to solve this was very interesting. Somehow I felt that LISP kind of directly addressed the problem we have on hand with very little emphasis on the structure of code. Ya the code was kinda wierd with tons of parenthesis, but succinct at the same time. We could just think of the problem that we were trying to solve rather than worry about whether the syntax for main() was right.

The solution for the Towers of Hanoi was done using a recursive process, and we were left with an excersise to try and see if we can do this the iterative way !!!

There was an interesting line that the professor said - " The key to solving complicated problems is to know what not to look at".
I thought this was a nice and simple way of saying what abstraction was all about, a very powerful statement at the same time cause this is a very important way of looking at problems.

Things are definitely picking up !!! As far as I can remember I think i remained conciousness thru the lecture :-)


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