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Tue Dec 9

  • Thu demos in 3rd floor elevator lobby
  • Handouts:
  • garbage collection
  • derived expressions (e.g. cond)
  • normal vs. applicative order
  • analyze

Thu Dec 4

  • more on metacirc: how environments work, persistence when defining in the environment, how a primitive bottoms out as a variable lookup to a binding in the-global-environment, driving around the interpreter from the listener, how user-defined procedures work.

Tue Dec 2

  • more on the metacircular evaluator: eval & apply, implementation of environments, and procedures
  • PS9 assigned
  • discussion of final projects

Tue Nov 25

Thu Nov 20

  • Quiz 3 administered

Tue Nov 18

  • ProjectProposal
  • Quiz 2 handed back & review
  • Quiz 3 topics
  • Project is due the last day of class, Thu Dec 11

Thu Nov 13

  • no class

Tue Nov 11

  • more streams

Thu Nov 6

  • Attach:streams-lecture-pt2.txt
  • Revised PS8.
  • Class final is Thu Dec 18 at 3 pm, room TBA.
  • Quiz 3 is Thu Nov 20.
  • No class on Tue Nov 11 - Veteran's Day.
  • No class on Thu Nov 13 -- work on your projects.

Tue Nov 4

  • Streams stuff! did cons-stream, stream-car, stream-cdr, stream-enumerate-interval, stream-filter. Saw how evaluating the stream-car forces the evaluation of the car element, and also mutates the stream. Discussed the memo-izatio process.
  • Assigned PS8.
  • Attach:stream-examples.ss

Thu Oct 30

Tue Oct 28

  • quiz 2 administered

Thu Oct 23

  • handed out PS7, OO notes document, PS4 & PS5 answers
  • attempted to understand speaker/lecturer/arrogant-lecturer object hierarchy
  • attempted missing environment diagram from OO notes document
  • prepped for quiz 2

Tue Oct 21

Thu Oct 16

Tue Oct 14

Thu Oct 9

  • Quiz 1

Tue Oct 7

(define (make-sum a1 a2)
  (cond ((=number? a1 0) a2)
	((=number? a2 0) a1)
	((and (number? a1) (number? a2)) (+ a1 a2))
        ((and (and (symbol? a1) (symbol? a2))
              (eqv? a1 a2))
         (make-product '2 a1))
	(else (list '+ a1 a2))))
  • Also did this in make-product such that (* x x) gets converted to (** x 2).
  • Noted that directly entering expressions such as '(+ x 3) is an abstraction violation; e.g., one should use (make-sum 'x 3) instead.

Thu Oct 2

Symbolic data and differentiation

Tue Sept 30

Thu Sept 25

Tue Sept 23

Thu Sept 18

  • lecture notes
  • scheme code
  • lists, cons, car, cdr, cons cells & printed representation
  • "cdr'ing down a list"
  • wrote list functions: length, length-iter, nth, last, and append
  • started to look at trees
  • PS1 back
  • PS2 collected
  • PS3 out

Tue Sept 16

  • clarified question 9 of PS2; added new problem 16
  • discussed higher-order procedures - sum with a, b, term, next args
  • attempted to describe how let can be implemented with lambda
  • created expnt procedure, which outputs a procedure to perform exponentiation

Thu Sept 11

  • discussed PS1 -- fred should fix problem 3 & substitution model
  • scheme numerics (see link below)
  • applicative order demo of fibonacci
  • recursive vs iterative processes
  • in-class working of 1st problems from PS2
  • intro to python
  • parens vs. indentation
  • infix vs. prefix vs. postfix
  • fred will post his office hrs

Tue Sept 9

  • please join class google group
  • introduced lists, incl. cons, car, and cdr
  • introduced lambda and naming functions
  • showed a function that accepts a function as input
  • looked at run-away recursive example
  • discussed substitution model of execution
  • looked at Scheme numerics, including big numbers and rational numbers -- how does it do it? See http://www.cs.grinnell.edu/~rebelsky/Courses/CS151/2003F/Readings/numbers.html.
  • PLT Scheme destroys the environment on recompile -- how can we stop this?

Thu Sept 4

  • read Paul Graham's essay in class
  • talked about 5 "big ideas" of the class