if(l==1|n==1|l==n){
return 1;
}else{
return recursion(l-1,n-1)+recursion(l-1,n);
}
}
public static void main(String[] args){
System.out.println(recursion(7,4));
}
]]>
((= x 1) 1)
((= x 2) 1)
((= y 1) 1)
((= x y) 1)
(else
(+ (Pascal(- x 1) y) (Pascal (- x 1) (- y 1))
))))
]]>
make install
鎴栨槸涓嶉噸鏂板畨瑁呯殑鎯呭喌涓嬶細
make WITH_PROXY_MODULE=yes
]]>
鎸傝澆錛?br /> mount -t smbfs -o username=administrator,password=pwdabc,iocharset=cpq36 //192.168.0.11/share /mnt/11share
]]>
recursive:
(define (fn n)
(cond ((>= n 3) (+ (+ (fn (- n 1)) (* 2 (fn (- n 2)))) (* 3 (fn (- n 3)))))
((< n 3) n)
))
iterative:
(define (re n)
(if (< n 3)
n
(iter 2 1 0 n)
))
(define (iter a b c n)
(if(= n 3)
(ca a b c)
(iter (ca a b c) a b (- n 1))
)
)
(define (ca a b c)
(+ a (* 2 b) (* 3 c) )
)
]]>
(x/y2+2y)/3
Use this formula to implement a cube-root procedure analogous to the square-root procedure. (In
section 1.3.4 we will see how to implement Newton's method in general as an abstraction of these
square-root and cube-root procedures.)
(define (cube x)
(* x x x))
(define (square x)
(* x x ))
(define (result x y)
(/ (+ (/ x (square y)) (* 2 y)) 3))
(define (improve x guess)
(result x guess))
(define (good-enough? x guess)
(< (abs (- (* guess guess guess ) x))0.001))
(define (sqrt-iter x guess)
(if (good-enough? x guess)
guess
(sqrt-iter x (improve x guess)
)))
]]>
Ator claims this can indeed be done, and she defines a new version of if:
(define (new-if predicate then-clause else-clause)
(cond (predicate then-clause)
(else else-clause)))
Eva demonstrates the program for Alyssa:
(new-if (= 2 3) 0 5)
5
(new-if (= 1 1) 0 5)
0
Delighted, Alyssa uses new-if to rewrite the square-root program:
32(define (sqrt-iter guess x)
(new-if (good-enough? guess x)
guess
(sqrt-iter (improve guess x)
x)))
What happens when Alyssa attempts to use this to compute square roots? Explain.
(define (new-if predicate then-clause else-clause)
(cond (predicate then-clause)
(else-clause)))
(define (average x y)
(/ (+ x y) 2))
(define (improve guess x)
(average guess (/ x guess)))
(define (good-enough? guess x)
(< (abs (- (square guess) x))0.001))
(define (square x)
(* x x))
(define (sqrt-iter guess x)
(new-if (good-enough? guess x)
guess
(sqrt-iter (improve guess x)
x)))
sqrt-iter (improve guess x)浣滀負鍙傛暟鏉ヤ紶閫掔粰new-if錛屽湪鎵цnew-if鐨勬椂鍊欙紝灝辨繪槸浼氭墽琛宻qrt-iter (improve guess x)錛岄犳垚浜嗘寰幆銆?br />
]]>
(define (compare x y) (- x y))
(define (sumsquares x y)(+(* x x)(* y y)))
(define (returnlarge a b c)
(cond ((and (>= (compare a b) 0) (>= (compare c b) 0)) (sumsquares a c))
((and (>= (compare a c) 0) (>= (compare b c) 0)) (sumsquares a b))
((and (>= (compare c a) 0) (>= (compare b a) 0)) (sumsquares b c))
)
)
(returnlarge 3 3 2)
>18
]]>
web.xml錛?br />
<listener>
<listener-class>com.com.ActiveUserListener2</listener-class>
</listener>
<distributable/>
ActiveUserListener2.java
package com.com;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class ActiveUserListener2 implements HttpSessionListener {
private static int sessionCount2 = 0;
private static Map sessionMaps2 = new HashMap(); //瀛樻斁session鐨勯泦鍚堢被
public void sessionCreated(HttpSessionEvent arg0) {
HttpSession session = arg0.getSession();
String sessionId = session.getId();
System.out.println("Create a session:" + sessionId);
sessionMaps2.put(sessionId, session);
sessionCount2++;
}
public void sessionDestroyed(HttpSessionEvent arg0) {
sessionCount2--;
String sessionId = arg0.getSession().getId();
sessionMaps2.remove(sessionId);//鍒╃敤浼氳瘽ID鏍囩ず鐗瑰畾浼氳瘽
System.out.println("Destroy a session:" + sessionId);
}
public static int getSessionCount() {
return sessionCount2;
}
public static Map getSessionMaps() {
return sessionMaps2;
}
}
浼犻抯essionid錛?jsessionid=<%=session.getId()%>
嫻嬭瘯鏁堟灉錛?br />
<%
Map activeSessions = ActiveUserListener2.getSessionMaps();
out.println(activeSessions.get("CB55ABC39DD5B917D65F456C28FC25E6.tomcat1"));
out.println(activeSessions);
}
}
%>
]]>