下推栈实现（c++编程思想 p136）

 1 #ifndef STACK_H
 2 #define STACK_H
 3 
 4 struct Stack
 5 {
 6 
 7     struct Link
 8     {
 9         void* data;
10         Link* next;
11         void initialize(void* dat, Link* nxt);
12     }* head;
13 
14     void initialize();
15     void push(void* dat);
16     void* peek();
17     void* pop();
18     void cleanup();
19 };
20 
21 #endif // STACK_H

 1 #include "Stack.h"
 2 #include "../require.h"
 3 
 4 using namespace std;
 5 
 6 void Stack::Link::initialize(void* dat, Link* nxt)
 7 {
 8     data = dat;
 9     next = nxt;
10 }
11 
12 void Stack::initialize()
13 {
14     head = 0;
15 }
16 
17 void Stack::push(void* dat)
18 {
19     Link *newLink = new Link;
20     newLink->initialize(dat, head);
21     head = newLink;
22 }
23 
24 void* Stack::peek()
25 {
26     require(head !=0, "Stack empty");
27     return head->data;
28 }
29 
30 
31 void* Stack::pop()
32 {
33     if (head == 0)
34         return 0;
35     void* result = head->data;
36     Link* oldHead = head;
37     head = head->next;
38     delete oldHead;
39     return result;
40 }
41 
42 
43 void Stack::cleanup()
44 {
45     require(head == 0, "Stack not empty");
46 }

 1 #include <iostream>
 2 #include <fstream>
 3 #include <string>
 4 #include "Stack.h"
 5 #include "../require.h"
 6 
 7 using namespace std;
 8 
 9 int main(int argc, char* argv[])
10 {
11 
12     requireArgs(argc, 1);
13 
14     ifstream in(argv[1]);
15     assure(in, argv[1]);
16 
17     Stack textLines;
18     textLines.initialize();
19 
20     string line;
21     while (getline(in, line)) //文件以行为单位入栈
22         textLines.push(new string(line));
23 
24     string* s;
25     while ((s = (string*) textLines.pop()) != 0) //出栈
26     {
27         cout << *s << endl;
28         delete s;
29     }
30 
31     textLines.cleanup();
32     return 0;
33 }

 1 #ifndef REQUIRE_H
 2 #define REQUIRE_H
 3 
 4 #include <cstdio>
 5 #include <cstdlib>
 6 #include <fstream>
 7 #include <string>
 8 
 9 inline void require(bool requirement, const std::string& msg = "Requirement failed")
10 {
11   using namespace std;
12   if (!requirement)
13   {
14     fputs(msg.c_str(), stderr);
15     fputs("\n", stderr);
16     exit(1);
17   }
18 }
19 
20 inline void requireArgs(int argc, int args, const std::string& msg = "Must use %d arguments")
21 {
22   using namespace std;
23    if (argc != args + 1)
24    {
25      fprintf(stderr, msg.c_str(), args);
26      fputs("\n", stderr);
27      exit(1);
28    }
29 }
30 
31 inline void requireMinArgs(int argc, int minArgs, const std::string& msg ="Must use at least %d arguments")
32 {
33   using namespace std;
34   if(argc < minArgs + 1)
35   {
36     fprintf(stderr, msg.c_str(), minArgs);
37     fputs("\n", stderr);
38     exit(1);
39   }
40 }
41 
42 inline void assure(std::ifstream& in, const std::string& filename = "")
43 {
44   using namespace std;
45   if(!in)
46   {
47     fprintf(stderr, "Could not open file %s\n",
48       filename.c_str());
49     exit(1);
50   }
51 }
52 
53 inline void assure(std::ofstream& out, const std::string& filename = "")
54 {
55   using namespace std;
56   if(!out) {
57     fprintf(stderr, "Could not open file %s\n",
58       filename.c_str());
59     exit(1);
60   }
61 }
62 
63 
64 #endif // REQUIRE_H