Common Lisp!

1
Common Lisp!

• John Paxton
• Montana State University
• Summer 2003

2
Montana National Parks

• Yellowstone
• Glacier

3
Structure Declaration

• (defstruct city
• name
• country
• (population 100000)
• )

4
Structure Creation

• gt (setf san-salvador (make-city))
• S(CITY NAME NIL COUNTRY NIL POPULATION
  100000)
• gt (setf bozeman (make-city population 30000))
• S(CITY NAME NIL COUNTRY NIL POPULATION 30000)

5
Field Access

• gt (setf (city-country san-salvador)
• 'el-salvador)
• EL-SALVADOR

6
Useful Predicates

• gt (city-p san-salvador)
• T
• gt (describe san-salvador)
• S(CITY NAME NIL COUNTRY EL-SALVADOR
  POPULATION 100000) is a structure of type CITY.
• Slots
• NAME NIL
• COUNTRY EL-SALVADOR
• POPULATION 100000 and more!

7
Questions

1. Declare a structure called playing-time that can
   hold the number of minutes and seconds that a
   song lasts.
2. Instantiate an instance of the above structure
   that plays for 3 minutes and 42 seconds.
3. Declare another structure called song that can
   hold the name of a song and its playing-time.

8
Questions

1. Instantiate an instance of this previous
   structure for the 1996 Los del Rio hit, Macarena,
   which plays for 3 minutes and 12 seconds.
2. Access the name of the song.
3. Access the playing-time of the song.
4. Declare an array that can hold 3 songs.
5. Assign the above structure to the second slot in
   the array.