CSC153 2004S, Class 13: Pause for Breath

Admin:
* Homework 3 due.
  * I'll treat the second part as extra credit.
* Homework 1 graded.
* Homework 2 & 3? to be graded tonight (I hope).
* Questions on the exam?
* Sam will be unavailable most of the weekend.
* How do you get disgusting colors in your program?
  * Click "check syntax"
  * Write a scheme->html translator
* In spite of what it says on the class outline, no reading for tomorrow.

Overview:
* Randomness
* Some notes on homework 1

* Why is (eq? 0.0 -0.0) false?
  * They occupy different memory locations.
  * Pedagogical tool: Use = for comparing numbers.
  * Assumption: If someone is silly enough to write -0.0, they obviosuly intend something different than 0.0.

/Random Lists/
* See random-sum.scm

/Notes on Homework 1/
* Please limit your work to seventy or so characters per line.
* Try *lots* of test cases.
  * There seems to be no difference between remainder and modulus (but there is)
  * Relationship between floor, ceiling, truncate, and round
    * floor: Find the largest integer less than or equal to its parameter
    * ceiling: Find the smallest integer greater than or equal to its parameter
    * (truncate val): "Returns the number to the left of the decimal point"
      Find the integer whose absolute value is the largest integer less than or equal to the absolute value of val
      * Wrong: (truncate -2.5) -> 2
      * (floor val) if val is positive, (ceiling val) if val is negative
    * (round val): "Follows standard rounding procedures"; Rounds to the nearest integer.
	(round 3.5) => 4
	(round 2.5) => 3 (nope, 2)
      * Rounds toward the even.  Why?