Artificial Intelligence Week 2 : SEARCH - LISP

최 윤 정

참고http://www.cs.cmu.edu/~dst/LispBook/index.html

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함수와 데이터

데이터 : 속성 , information 수 (number), 단어 (word) , 이들의 리스트

interger, float, ratio( 비율 ), string , list

함수 : 기능 , 역할

입력된 데이터로 결과 (result) 를 만들어 내는 box

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int add(int i, int j){

return i+j ;}

int divide(int i, int j){

return i/j ;} // 인자의 순서도 중요

함수와 데이터

심볼 (symbol) : Lisp 의 데이터 타입중 하나

Sequence of letter , digits and special characters X, My-name, THREE-IS-3 Special symbols :

T : logical True, Yes NIL: logical False, No, Emptiness

술어 (Predicate) : 질문 - 답변 함수

결과가 True 면 T, False 면 Nil 을 return 기본 build-in 함수들

NUMBERP, SYMBOLP, EQUAL, ODDP,EVENP .. 등

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FOUR : symbol4 : integer+4 : integer+ : symbol7-11 : symbol

Combination function +, add1, add2

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List Most versatile data type ( ) 로 둘러 쌓인 item 들의 묶음

A : symbol, (A) : list (a b c), (1 2 3), ( I Love You) 실제 pointer 를 사용한 cons cell 의 연결구조 (NIL 을 가리키는 cell 이 마지막 요소 )

(RED GREEN BLUE)

( (BLUE SKY) (GREEN GRASS) (BROWN EARTH))

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Exercise

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List 함수 : LENGTH Length : Top-level 의 cons cell 개수

(A (B C) D) : A , ( B C) , D 3 (A (B C) (D E F) ) : 3 ( ) = NIL = empty list : 0 NIL : symbol 이면서 list

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3

EQUAL

(A (B C) D) 와 (A B (C D)) 는 다름 ! 길이와 내부구조 , 순서가 모두 같을 때만 같음 .

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Exercise

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FIRST, SECOND, THIRD, and REST

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Return a Pointer

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CAR and CDR

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Combination

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Exercise

( (A B) (C D) (E F ))

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>>(setq x '( (a b) ( c d ) (e f )))>>(car x) >>(car (car (cdr x))) C>>(cdr (car (cdr x))) (D)

CONS : Create a new cons cell

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Cons : Nonlist structure (A B C . D)

#1 = (#1# . A)

#1 = ( A B C . #1#)

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Exercise

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LIST : creating a list

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Exercise

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EVAL notation (* 3 (+ 5 6) )

(Oddp ( + 1 6))

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Define Function in EVAL Notation

( defun average ( x y) ( / ( + x y)

2.0) )

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Symbols and Lists as Data Evaluating symbols

pi : 3.14159 , Build-in variable ! Eggplant : ERROR! , unassigned variable

Quote : ‘ (equal kim park) : ERROR! Unassigned variable. (equal ‘kim ‘park) : nil

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3-ways to make lists

1. ( cons ‘a ‘(b c)) : (a b c) 2. ( list ‘a ‘b ‘c) : (a b c)

3.

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Exercise

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Review Exercise

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Don’t parenthesize variables in the argument list; don’t quote variables;

LISP on Computer

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Read-Eval-Print Loop Listener 에서

수정 : ctrl - G

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defun : define function

But , The most frequently occurring errors in LISP are parenthetical errors. It

is thus almost imperative to employ some sort of counting or pairing device to check parentheses every time that a function is changed.

— Elaine Gord, ‘‘Notes on the debugging of LISP programs,’’ 1964.

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Setf : assign a value to a variable > (setf x ’(a b c))(A B C)

> (setf y (cons ’d (cdr x)))(D B C)

> x (A B C)

> y (D B C)

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HEAD, TAIL, and LONG-LIST are all global variables.

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COND : if

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