Читать «Справочное руководство по C++» онлайн - страница 108
Бьярн Страустрап
case '*':
case '/':
case '+':
case '-':
case '(':
case ')':
case '=':
return curr_tok=ch;
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
case '.':
cin.putback(ch);
cin ›› number_value;
return curr_tok=NUMBER;
default:
if (isalpha(ch)) {
char* p = name_string;
*p++ = ch;
while (cin.get(ch) && isalnum(ch)) *p++ = ch;
cin.putback(ch);
*p = 0;
return curr_tok=NAME;
}
error ("bad token");
return curr_tok=PRINT;
}
}
int main(int argc, char* argv[])
{
switch (argc) {
case 1:
break;
case 2:
cin = *new istream(strlen(argv[1]),argv[1]);
break;
default:
error("too many arguments");
return 1;
}
// insert predefined names:
insert("pi")-›value = 3.1415926535897932385;
insert("e")-›value = 2.7182818284590452354;
while (1) {
get_token();
if (curr_tok == END) break;
if (curr_tok == PRINT) continue;
cout ‹‹ expr() ‹‹ "\n";
}
return no_of_errors;
}
b3_2_6a.cxx
extern void strcpy(char *,char *);
extern void exit(int);
extern int strlen(char *);
char *save_string(char* p)
{
char* s = new char[strlen(p)+1];
strcpy(s,p);
return s;
}
int main (int argc, char* argv[])
{
if (argc ‹ 2) exit(1);
int size = strlen(argv[1])+1;
char* p = save_string (argv[1]);
delete[size] p;
}
b3_2_6b.cxx
#include ‹stream.hxx›
extern void exit(int);
void out_of_store()
{
cout ‹‹ "operator new failed: out of store\n";
exit(1);
}
typedef void (*PF)();
extern PF set_new_handler(PF);
main()
{
set_new_handler(&out_of_store);
char *p = new char[100000000];
cout ‹‹ "done, p = " ‹‹ long(p) ‹‹ "\n";
}
b4_6_8.cxx
// This version of the program does not assume sizeof(int) == sizeof(char*)!
#include ‹stream.hxx›
#include ‹stdarg.hxx›
extern void exit(int);
void error (int …);
main(int argc, char* argv[])
{
switch (argc) {
case 1:
error(0,argv[0],(char*)0);
break;
case 2:
error(0,argv[0],argv[1],(char*)0);
break;
default:
error(1,"with",dec(argc-1),"arguments",(char*)0);
}
}
void error(int n …)
{
va_list ap;
va_start(ap,n);
for (;;) {
char *p = va_arg(ap,char*);
