cout.flag()

非常抱歉，我之前的回答有误，实际上 `cout.flag()` 这个函数是不存在的，正确的函数名是 `cout.flags()`。这个函数用于获取或设置输出流的格式化标志，例如设置小数点后保留几位、输出负数标志等等。调用方式为：

1. 获取当前格式化标志：`cout.flags()`
2. 设置新的格式化标志：`cout.flags(new_flags)`

其中，`new_flags` 是一个标志位的组合，可以通过以下方式指定：

1. 使用 `ios::` 命名空间下的标志位，例如 `ios::fixed`、`ios::scientific`、`ios::showpos` 等等。
2. 多个标志位可以通过按位或运算符 `|` 进行合并，例如 `ios::fixed | ios::showpoint`。

需要注意的是，`cout.flags()` 返回的是一个 `ios_base::fmtflags` 类型的值，如果需要解析这个值中包含的标志位，可以使用 `ios::flags()` 函数。

相关问题

struct node { string str;//flag =0 double num;//flag =1 int flag; }; stack<node> SEM; int t_value ; void CEQ(char ch) {//四元式 t_value++; char t_value_char = '0' + t_value; string t = "t"; t.append(1, t_value_char); node m1 = SEM.top(); SEM.pop(); node m2 = SEM.top(); SEM.pop(); cout << "(" << ch << " "; if (m2.flag == 0) { cout << m2.str; } if (m2.flag == 1) { cout << m2.num; } cout << ","; if (m1.flag == 0) { cout << m1.str ; } if (m1.flag == 1) { cout << m1.num ; } cout<<","<<t<<")"<<endl; node m3; m3.flag = 0; m3.str = t; SEM.push(m3); }

这段代码定义了一个结构体 `node`，其中包含一个字符串和一个浮点数，以及一个整型标志 `flag`。另外还定义了一个 `stack` 对象 `SEM`，用于存储 `node` 类型的数据。还有一个整型变量 `t_value` 和一个 `void` 类型的函数 `CEQ`。

函数 `CEQ` 接收一个字符参数 `ch`，用于表示要执行的操作。函数中首先对 `t_value` 进行自增操作，并将其转换为字符类型。然后创建一个字符串 `t`，并在其后面添加一个字符 `t_value_char`，用于表示临时变量名。

接着从 `SEM` 中取出两个 `node` 类型的数据 `m1` 和 `m2`，并打印出对应的四元式。最后创建一个新的 `node` 类型的数据 `m3`，将其标志设置为 0，字符串设置为 `t`，并将其压入 `SEM` 中。

这段代码中的 `CEQ` 函数用于生成中间代码的四元式。

Q21: Which of the following is a valid user-defined output stream manipulator header? a. ostream& tab( ostream& output ) b. ostream tab( ostream output ) c. istream& tab( istream output ) d. void tab( ostream& output ) Q22: What will be output by the following statement? cout << showpoint << setprecision(4) << 11.0 << endl; a. 11 b. 11.0 c. 11.00 d. 11.000 Q23: Which of the following stream manipulators causes an outputted number’s sign to be left justified, its magnitude to be right justified and the center space to be filled with fill characters? a. left b. right c. internal d. showpos Q24: Which of the following statements restores the default fill character? a. cout.defaultFill(); b. cout.fill(); c. cout.fill( 0 ); d. cout.fill( ' ' ); Q25: When the showbase flag is set: a. The base of a number precedes it in brackets. b. Decimal numbers are not output any differently. c. "oct" or "hex" will be displayed in the output stream. d. Octal numbers can appear in one of two ways. Q26: What will be output by the following statements? double x = .0012345; cout << fixed << x << endl; cout << scientific << x << endl; a. 1.234500e-003 0.001235 b. 1.23450e-003 0.00123450 c. .001235 1.234500e-003 d. 0.00123450 1.23450e-003 Q27: Which of the following outputs does not guarantee that the uppercase flag has been set? a. All hexadecimal numbers appear in the form 0X87. b. All numbers written in scientific notation appear the form 6.45E+010. c. All text outputs appear in the form SAMPLE OUTPUT. d. All hexadecimal numbers appear in the form AF6. Q28: Which of the following is not true about bool values and how they're output with the output stream? a. The old style of representing true/false values used -1 to indicate false and 1 to indicate true. b. A bool value outputs as 0 or 1 by default. c. Stream manipulator boolalpha sets the output stream to display bool values as the strings "true" and "false". d. Both boolalpha and noboolalpha are “sticky” settings.

A21: a. ostream& tab( ostream& output ) is a valid user-defined output stream manipulator header.

A22: c. 11.00 will be output by the statement.

A23: c. internal is the stream manipulator that causes an outputted number’s sign to be left justified, its magnitude to be right justified and the center space to be filled with fill characters.

A24: d. cout.fill(' ') restores the default fill character, which is a space.

A25: c. "oct" or "hex" will be displayed in the output stream when the showbase flag is set.

A26: b. 1.23450e-003 and 1.23450e-003 will be output by the statements.

A27: d. All hexadecimal numbers appearing in the form AF6 does not guarantee that the uppercase flag has been set.

A28: a. The old style of representing true/false values used -1 to indicate false and 1 to indicate true is not true. False is represented by 0 and true is represented by any non-zero value.