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Preface
Part I
Chap 1
Chap 2
Chap 3
XEmacs
Chap 4
Chap 5
Chap 6
Chap 7
Chap 8
Chap 9
Part II
Chap 10
Chap 11
Chap 12
Chap 13
Chap 14
Chap 15
Chap 16
Chap 17
Chap 18
Chap 19
Chap 20
Chap 21
Chap 22
Chap 23
Part III
Chap 24
Chap 25
Chap 26
Chap 27
Chap 28
Chap 29
Chap 30
Chap 31
Chap 32
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CHAPTER 29: INPUT/OUTPUT
- Corrections
-
- Page 217, line 4: Change interaction
to interactions.
- Page 217, line 13: Change evaluate form
to evaluate a form.
- Page 225, line -10: Change (format t " &I
heard you say A " sentence) to (format t "~&I heard you say ~{~A~}"
sentence).
- Page 227, line -3 - page 228, line 3: Instead of using
provide and require, put (unless
(find-package 'match) (load match) as the first form in your
eliza file, even before the defpackage form.
- Notes
-
- Read Chapter 29.
- On the last line of page 218 and the first line of page 219,
I say "A common mistake is forgetting that these functions take only
one argument." For example,
(print 'Hello 'Frank) will
produce an error. However, it won't be the error you might expect.
Actually, the print functions take a second, optional argument, which
must be a stream. A stream is a generalized file, and includes the
standard output file. So the error message will tell you that
FRANK is not a stream. A nickname for the standard
output stream, which is the default value of the optional argument, is
the symbol T, so (print 'Hello t) will do
exactly the same thing as (print 'Hello).
- On page 221, I say that the first argument of
format, which I call destination, is
either t or nil, and in the footnote, I say
that there are other possibilities. Actually
destination must evaluate to a stream, and as I
said above, the symbol t is a nickname for the standard
output stream. nil is a special case as a
destination for format. The other possibilities
are other streams, but we will still not discuss streams any more in
this course.
- Do Exercises 29.1 - 29.7. These exercises are valuable for
learning how the Common Lisp we are using behaves when reading input.
- Do Exercise 29.8 to learn about two valuable functions for
output.
- Do Exercises 29.9 - 29.16. These are valuable for learning
how to write an interactive program that prompts its user for input.
- Exercise 29.13 introduces the function
values.
I mentioned in the footnote on page 169 that "Common Lisp provides a
facility that can be used to have a function return more than one
value". This facility is the values function, which can
be given zero or more arguments, and returns them all. To see it
work, evaluate the following:
(values)
(values 'a)
(values 'a (+ 2 5))
(values 'a (+ 2 5) (second '(a b c)))
We will still not discuss this feature any more in this course.
- Exercises 29.14 - 29.16 are to learn more about the printing
functions.
- Exercises 29.17 - 29.22 are valuable for learning about the
format function. This is the most flexible and useful
Common Lisp printing function, and is similar to C's
writef.
- Exercises 29.23 - 29.31 are valuable for learning to write
Lisp interactive programs. In particular, Exercises 29.29 - 29.31
discuss versions of the "echo" program.
- In your
match file, define a function
(apply-rules-fully tree rule-list)
This should apply the first rule on rule-list to
tree, then apply it again to the result, etc., until it
doesn't apply any more. Then it should apply the second rule to the
result until it doesn't apply any more, etc. for all the rules on
rule-list. For example, the following rules
((($x you $y) ($x origyou $y))
(($x I $y) ($x you $y))
(($x me $y) ($x you $y))
(($x origyou $y) ($x me $y)))
will change all occurrences of I and me to
you, and all occurrences of you to
me.
- In your
match file, define a function
(apply-one-rule tree rule-list)
This should try the rules on rule-list in order, and when
the first applies to tree, apply the rule and return the result.
- Make
apply-rules-fully and
apply-one-rule external symbols in the match
package.
- Create a file named
eliza.cl. The first form
in this file should be
(unless (find-package 'match) (load "match"))
Next put the defpackage and in-package forms
so that the rest of the file will be in the eliza
package. Put a (:use common-lisp match) subform in the
defpackage form, so that you can use exported symbols
from the match package without qualification in the
eliza package. (See page 81.)
- In your
eliza.cl file, define the
function eliza to print an informative message, and then
be a read-eval-print loop that reads sentences from the
user and:
- uses
apply-rules-fully to apply manditory rules to
the user's sentences, such as those that change "I" to "you";
- uses
apply-one-rule to further transform the
user's sentences into replies;
- prints the reply, without any enclosing parentheses, and
followed by a newline.
- Make
eliza an external symbol of the eliza
package.
- Create two sets of rules for your eliza to use. Suggestions
of manditory rules are above in the section on
apply-rules-fully.
Suggestions for the other set of rules are in the text on page 227.
Since apply-one-rule tries rules in order, you can end
the list of rules with a very general one like
($x (Tell me more.))
or
($x (Very interesting.))
You can get additional ideas by evaluating M-x doctor in
your XEmacs, and interacting with the version of Eliza there.
- Make the last form in your
eliza.cl file the
form (eliza) so that your eliza function is
called as soon as your eliza file is loaded.
- Note the following problem: Your users will probably be in
the
user package when they load your eliza
file. Since the final form of your file is a call to the
eliza function, the interaction with your users will be
in the eliza package, and everything should go well.
However, if they should exit your eliza function, and try
to reenter it by executing (eliza:eliza), they will then
be interacting in the
user package, and that will make your rules fail. Here's
how to fix this:
Wrap the read-eval-print loop of your
eliza function in a let with the variable
*package* set to (find-package 'eliza), and
declare *package* to be special. That way,
you will read your users' sentences in the eliza package,
and they will return to their original package when eliza
terminates.
- Submit your enhanced
match.cl file and your
eliza.cl file.
- Create and submit a file
ch29.cl containing
a demonstration interaction with your Eliza.
- When you have submitted correct exercises through this
chapter, you will have finished your project, and earned a grade of
A. Congratulations!
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