Class 21: CGI Scripting

Held Friday, September 29, 2000

Summary

Today we consider how to turn Scheme data into HTML.

Notes

• Exam 1 is due today.
  • I probably won't return it next week, although I may make an answer key available.
  • I hear that the phrase ``this is the hardest exam I've ever taken'' does in fact apply to this exam.
• Think about the project over the weekend (in particular, think about how you might look up values in our ``database'').
• Enjoy the cookies and fruit once lab starts.

Overview

• Project discussion
• Displaying ``records''
• Laboratory: Displaying records in our database

What Is Our Project?

• What topic?
  • Dating game?
  • Stress relief?
  • Music recommendation system?
• Jonathan and I both think a dating system would be somewhat fun.
• Once we've decided on a project, we need to think about what data we'll store for each entry.

Displaying Information as Text

• This example comes from Tuesday's class. We'll display a person in useful form.
• Recall that a person has the form
  (name eyecolor haircolor favecolor)
• First, some helper functions

  (define person-name 
    (lambda (person) (car person)))
  (define person-eyes
    (lambda (person (cadr person))))
  (define person-hair
    (lambda (person (caddr person))))
  (define person-fave
    (lambda (person (cadddr person))))
  

• Note that we might also have used the more compact

  (define person-name car)
  (define person-eyes cadr)
  (define person-hair caddr)
  (define person-fave cadddr)
  

• Now, let's display info on a person

  (define summarize-person
    (lambda (person)
      (display "Vital statistics for ")
      (display (person-name person))
      (newline)
      (display "  Eyes are ")
      (display (person-eyes person))
      (newline)
      (display "  Hair is ")
      (display (person-hair person))
      (newline)
      (display "  Favorite color is ")
      (display (person-fave person))
      (newline)
      (display "Doesn't this just make you want to love ")
      (display (person-name person))
      (display "?")
      (newline)))
  

• And let's test it out.

  > (summarize-person '(Michelle reddish-brown hazel red))
  Vital statistics for michelle
    Eyes are reddish-brown
    Hair is hazel
    Favorite color is red
  Doesn't this just make you want to love michelle?
  

Today's Exercises

a. Write the equivalent of summarize-person for our database.

b. Test it on sample data.

c. Write a similar procedure that generates HTML instead of plain text.