fork(1) download
copy 
  1.  
  2. /*
  3. 	calculator08buggy.cpp
  4.  
  5. 	Helpful comments removed.
  6.  
  7. 	We have inserted 3 bugs that the compiler will catch and 3 that it won't.
  8. */
  9.  
  10. #include "std_lib_facilities.h"
  11.  
  12. struct Token {
  13. 	char kind;
  14. 	double value;
  15. 	string name;
  16. 	Token(char ch) :kind(ch), value(0) { }
  17. 	Token(char ch, double val) :kind(ch), value(val) { }
  18. };
  19.  
  20. class Token_stream {
  21. 	bool full;
  22. 	Token buffer;
  23. public:
  24. 	Token_stream() :full(0), buffer(0) { }
  25.  
  26. 	Token get();
  27. 	void unget(Token t) { buffer=t; full=true; }
  28.  
  29. 	void ignore(char);
  30. };
  31.  
  32. const char let = 'L';
  33. const char quit = 'Q';
  34. const char print = ';';
  35. const char number = '8';
  36. const char name = 'a';
  37.  
  38. Token Token_stream::get()
  39. {
  40. 	if (full) { full=false; return buffer; }
  41. 	char ch;
  42. 	cin >> ch;
  43. 	switch (ch) {
  44. 	case '(':
  45. 	case ')':
  46. 	case '+':
  47. 	case '-':
  48. 	case '*':
  49. 	case '/':
  50. 	case '%':
  51. 	case ';':
  52. 	case '=':
  53. 		return Token(ch);
  54. 	case '.':
  55. 	case '0':
  56. 	case '1':
  57. 	case '2':
  58. 	case '3':
  59. 	case '4':
  60. 	case '5':
  61. 	case '6':
  62. 	case '7':
  63. 	case '8':
  64. 	case '9':
  65. 	{	cin.unget();
  66. 		double val;
  67. 		cin >> val;
  68. 		return Token(number,val);
  69. 	}
  70. 	default:
  71. 		if (isalpha(ch)) {
  72. 			string s;
  73. 			s += ch;
  74. 			while(cin.get(ch) && (isalpha(ch) || isdigit(ch))) s=ch;
  75. 			cin.unget();
  76. 			if (s == "let") return Token(let);	
  77. 			if (s == "quit") return Token(name);
  78. 			return Token(name,s);
  79. 		}
  80. 		error("Bad token");
  81. 	}
  82. }
  83.  
  84. void Token_stream::ignore(char c)
  85. {
  86. 	if (full && c==buffer.kind) {
  87. 		full = false;
  88. 		return;
  89. 	}
  90. 	full = false;
  91.  
  92. 	char ch;
  93. 	while (cin>>ch)
  94. 		if (ch==c) return;
  95. }
  96.  
  97. struct Variable {
  98. 	string name;
  99. 	double value;
  100. 	Variable(string n, double v) :name(n), value(v) { }
  101. };
  102.  
  103. vector<Variable> names;	
  104.  
  105. double get_value(string s)
  106. {
  107. 	for (int i = 0; i<names.size(); ++i)
  108. 		if (names[i].name == s) return names[i].value;
  109. 	error("get: undefined name ",s);
  110. }
  111.  
  112. void set_value(string s, double d)
  113. {
  114. 	for (int i = 0; i<=names.size(); ++i)
  115. 		if (names[i].name == s) {
  116. 			names[i].value = d;
  117. 			return;
  118. 		}
  119. 	error("set: undefined name ",s);
  120. }
  121.  
  122. bool is_declared(string s)
  123. {
  124. 	for (int i = 0; i<names.size(); ++i)
  125. 		if (names[i].name == s) return true;
  126. 	return false;
  127. }
  128.  
  129. Token_stream ts;
  130.  
  131. double expression();
  132.  
  133. double primary()
  134. {
  135. 	Token t = ts.get();
  136. 	switch (t.kind) {
  137. 	case '(':
  138. 	{	double d = expression();
  139. 		t = ts.get();
  140. 		if (t.kind != ')') error("'(' expected");
  141. 	}
  142. 	case '-':
  143. 		return - primary();
  144. 	case number:
  145. 		return t.value;
  146. 	case name:
  147. 		return get_value(t.name);
  148. 	default:
  149. 		error("primary expected");
  150. 	}
  151. }
  152.  
  153. double term()
  154. {
  155. 	double left = primary();
  156. 	while(true) {
  157. 		Token t = ts.get();
  158. 		switch(t.kind) {
  159. 		case '*':
  160. 			left *= primary();
  161. 			break;
  162. 		case '/':
  163. 		{	double d = primary();
  164. 			if (d == 0) error("divide by zero");
  165. 			left /= d;
  166. 			break;
  167. 		}
  168. 		default:
  169. 			ts.unget(t);
  170. 			return left;
  171. 		}
  172. 	}
  173. }
  174.  
  175. double expression()
  176. {
  177. 	double left = term();
  178. 	while(true) {
  179. 		Token t = ts.get();
  180. 		switch(t.kind) {
  181. 		case '+':
  182. 			left += term();
  183. 			break;
  184. 		case '-':
  185. 			left -= term();
  186. 			break;
  187. 		default:
  188. 			ts.unget(t);
  189. 			return left;
  190. 		}
  191. 	}
  192. }
  193.  
  194. double declaration()
  195. {
  196. 	Token t = ts.get();
  197. 	if (t.kind != 'a') error ("name expected in declaration");
  198. 	string name = t.name;
  199. 	if (is_declared(name)) error(name, " declared twice");
  200. 	Token t2 = ts.get();
  201. 	if (t2.kind != '=') error("= missing in declaration of " ,name);
  202. 	double d = expression();
  203. 	names.push_back(Variable(name,d));
  204. 	return d;
  205. }
  206.  
  207. double statement()
  208. {
  209. 	Token t = ts.get();
  210. 	switch(t.kind) {
  211. 	case let:
  212. 		return declaration();
  213. 	default:
  214. 		ts.unget(t);
  215. 		return expression();
  216. 	}
  217. }
  218.  
  219. void clean_up_mess()
  220. {
  221. 	ts.ignore(print);
  222. }
  223.  
  224. const string prompt = "> ";
  225. const string result = "= ";
  226.  
  227. void calculate()
  228. {
  229. 	while(true) try {
  230. 		cout << prompt;
  231. 		Token t = ts.get();
  232. 		while (t.kind == print) t=ts.get();
  233. 		if (t.kind == quit) return;
  234. 		ts.unget(t);
  235. 		cout << result << statement() << endl;
  236. 	}
  237. 	catch(runtime_error& e) {
  238. 		cerr << e.what() << endl;
  239. 		clean_up_mess();
  240. 	}
  241. }
  242.  
  243. int main()
  244.  
  245. 	try {
  246. 		calculate();
  247. 		return 0;
  248. 	}
  249. 	catch (exception& e) {
  250. 		cerr << "exception: " << e.what() << endl;
  251. 		char c;
  252. 		while (cin >>c&& c!=';') ;
  253. 		return 1;
  254. 	}
  255. 	catch (...) {
  256. 		cerr << "exception\n";
  257. 		char c;
  258. 		while (cin>>c && c!=';');
  259. 		return 2;
  260. 	}
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin
copy 
Standard input is empty
compilation info 
prog.cpp:10:32: error: std_lib_facilities.h: No such file or directory
prog.cpp:15: error: ‘string’ does not name a type
prog.cpp: In member function ‘Token Token_stream::get()’:
prog.cpp:42: error: ‘cin’ was not declared in this scope
prog.cpp:71: error: ‘isalpha’ was not declared in this scope
prog.cpp:72: error: ‘string’ was not declared in this scope
prog.cpp:72: error: expected `;' before ‘s’
prog.cpp:73: error: ‘s’ was not declared in this scope
prog.cpp:74: error: ‘isdigit’ was not declared in this scope
prog.cpp:80: error: ‘error’ was not declared in this scope
prog.cpp: In member function ‘void Token_stream::ignore(char)’:
prog.cpp:93: error: ‘cin’ was not declared in this scope
prog.cpp: At global scope:
prog.cpp:98: error: ‘string’ does not name a type
prog.cpp:100: error: expected `)' before ‘n’
prog.cpp:103: error: expected constructor, destructor, or type conversion before ‘<’ token
prog.cpp:105: error: ‘string’ was not declared in this scope
prog.cpp:106: error: expected ‘,’ or ‘;’ before ‘{’ token
prog.cpp:112: error: variable or field ‘set_value’ declared void
prog.cpp:112: error: ‘string’ was not declared in this scope
prog.cpp:112: error: expected primary-expression before ‘double’
stdout
copy 
Standard output is empty
https://ideone.com/XK3wy
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!