Chapter 3 Practical: A Simple Database

前説

この章では、functions, macros and special operators の違いは気にするなと。


CDs and Records

symbolは、まあ名前。
keyword symbolは、symbolのうち、":"から始まるもの。


Filing CDs

特記事項なし。


Looking at the Database Contents

formatって、エラくLoopするな。試す。

CL-USER> (list *db* *db*)
(((:TITLE "Home" :ARTIST "Dixie Chicks" :RATING 9 :RIPPED T)
  (:TITLE "Fly" :ARTIST "Dixie Chicks" :RATING 8 :RIPPED T)
  (:TITLE "Roses" :ARTIST "kathy Mattea" :RATING 7 :RIPPED T))
 ((:TITLE "Home" :ARTIST "Dixie Chicks" :RATING 9 :RIPPED T)
  (:TITLE "Fly" :ARTIST "Dixie Chicks" :RATING 8 :RIPPED T)
  (:TITLE "Roses" :ARTIST "kathy Mattea" :RATING 7 :RIPPED T)))
CL-USER> (format t "~{~a:~10t~a~%~}~%" (list *db* *db*))
((TITLE Home ARTIST Dixie Chicks RATING 9 RIPPED T)
 (TITLE Fly ARTIST Dixie Chicks RATING 8 RIPPED T)
 (TITLE Roses ARTIST kathy Mattea RATING 7 RIPPED T)): ((TITLE
                                                         Home
                                                         ARTIST
                                                         Dixie Chicks
                                                         RATING
                                                         9
                                                         RIPPED
                                                         T)
                                                        (TITLE
                                                         Fly
                                                         ARTIST
                                                         Dixie Chicks
                                                         RATING
                                                         8
                                                         RIPPED
                                                         T)
                                                        (TITLE
                                                         Roses
                                                         ARTIST
                                                         kathy Mattea
                                                         RATING
                                                         7
                                                         RIPPED
                                                         T))

NIL
CL-USER>

なる。修正。

CL-USER> (format t "~{~{~{~a:~10t~a~%~}~%~}~}" (list *db* *db*))
TITLE:    Home
ARTIST:   Dixie Chicks
RATING:   9
RIPPED:   T

TITLE:    Fly
ARTIST:   Dixie Chicks
RATING:   8
RIPPED:   T

TITLE:    Roses
ARTIST:   kathy Mattea
RATING:   7
RIPPED:   T 

TITLE:    Home
ARTIST:   Dixie Chicks
RATING:   9
RIPPED:   T

TITLE:    Fly
ARTIST:   Dixie Chicks
RATING:   8
RIPPED:   T

TITLE:    Roses
ARTIST:   kathy Mattea
RATING:   7
RIPPED:   T

NIL

なんぞ。

これ、ミニ言語なんですね。


Improving the User Interaction

CL-USER> (defun prompt-read (prompt)
           (format *query-io* "~a: " prompt)
           (force-output *query-io*)
           (read-line *query-io*))
PROMPT-READ

*query-io*って?
REPLで調べると、TWO-WAY-STREAM なんですね。


Saving and Loading the Database

read/print equivalenceを保証するには、with-standard-io-syntaxを使う。

疲れがでてきたので、休憩。