Held: Monday, 2 May 2016

Back to Outline 48 - Association Lists. On to Outline 50 - An Introduction to Sorting.

Summary

We continue our explorations of binary search, grounding our explorations in practice.

Related Pages

• Reading: Searching
• Lab: Binary Search
• EBoard 49 (Source 49)

Overview

• Exploring the search API.
• Remaining questions.

Administrivia

• New partners.
• The food I brought for today seems to have disappeared.

Reminders

• Office hours this week
  • See http://rebelsky.youcanbook.me.
  • Ask me about other available times.
• Tutor hours
  • Sunday, 3-5 p.m.
  • Sunday-Thursday, 7-10 p.m.
• Review Sessions
  • Wednesday at 8pm in CS commons with Sarah
  • Thursday at 10 am with SamR
  • Thursday at 8pm in CS commons with Kumar

Upcoming Work:

• NO READING FOR TUESDAY!
• Lab Writeup:
  • Send email titled CSC 151 Lab Writeup 49 (Your Names)
  • Do not include the underscores.
  • Send to CSC151-02-grader@grinnell.edu
  • Due before class on Monday.
• Projects due tomorrow night.
• Exam 4 to be distributed tomorrow.

Extra Credit

• Send your reports to rebelsky@grinnell.edu with subject "CSC 151 Extra Credit". (Do not include the quotation marks.)
• Send opportunities to me before class with subject "CSC 151 EXTRA CREDIT OPPORTUNITY!"

Academic / Artistic

• Scholars' Convocation: Dutch Global Horizons, Thursday, April 28, 11 am, JRC 101
• Damon Williams: Bigger Than The Cops, April 28, 4pm or 5:15 pm
• Met Opera, Saturday, April 30, talk at 11:30, Opera at noon.

Peer

• Friday, Break Beat Poets performing behind Eco House at 4:30 p.m.
  • Eco house is across from Cleveland.
• Maybe GMon, Thursday, 7:30 p.m., Loose Lounge.
• Rushdie's East/West, May 6/7 at 7:30 p.m.

Regular Peer

• Social Dance Workshop Tuesdays 7:00-8:00 in Bucksbaum Dance Studio
• Post-break ExCo on British Politics Wednesdays at 8:00 in JRC 203.
  Just show up; you don't need to sign up.
• Pun club Saturdays at 4pm in Younker
• Electronic Potpourri on KDIC Fridays at Five
• Space Odyssey KDIC Fridays at Six
• Bollywood, Fridays, 7:30-8:30, Younker
• Effective Altruism club, 2:30-3:30 Sundays in JRC 226.

Misc

Not for Extra Credit

• Third year students, design a logo or something for a vinyl sticker.
  Earn a gift card to PC! (And a bag-o-stickers!) Deadline Friday.

Exploring the Search API

Suppose we have data for various students on campus: Last Name (string), First Name (string), Graduation Year (integer), Box Number (integer), and Phone number (string). We might search by any of the four criteria (and by other criteria) and we might therefore order in various ways.

(define people
  (vector 
    ("Aanderson" "Aan"    2017 4114 "x4410")
    ("Brown"     "Bruin"  2016 8123 "x9000")
    ("Doe"       "J"      2018 9999 "none")
    ("Smith"     "Kieran" 2015 4112 "x9231")
    ("Taylor"    "Mic"    2017 1234 "x0001")))

• Right now, we have things sorted by last name (and, surprisingly, by first name), so we might search by last name (or by first name).
• If we wanted to search by year, we'd order by year (although that's not likely to give particularly useful results).
• If we wanted to search by box number, we'd order by box number.
• Our search algorithm needs to know how to find the key in an entry
  • Last name: car
  • First name: cadr
  • Year: caddr
  • Box number: cadddr
• Our search algorithm needs to know how the keys are ordered
  • Traditionally, strings are ordered alphabetically
  • Traditionally, numbers are ordered numerically, from smallest to largest
• So our binary search algorithm needs four parameters:
  • The vector to search
  • The key to search for
  • The instructions for getting a key from each element
  • The mechanism used to order the elements
• All of this is a bit more complicated if we have a compound key, such as "last name plus first name plus phone number"

Lab

• Do the lab
• Be prepared to reflect.