linux - 关于 Pascal 输出的一些茫然

Question

平台:Linux 2.6.18 x86_64

编译器:适用于 x86_64 的 Free Pascal 编译器版本 2.2.2 [2008/11/05]

源代码为:

Program main;
var invalue:string;
Begin
        (*Until the EOF, this loop continue to work*)
        while not eof do
        begin
                Write('Please input the express: ');
                Flush(StdOut);
                Readln(invalue);
                Writeln('The expression is: ',invalue);
        end;
        Writeln('');
        Writeln('Exit the program. Bye!');
End.

我编译并运行了它。但输出是这样的:

123
Please input the express: The expression is: 123
234
Please input the express: The expression is: 234
345
Please input the express: The expression is: 345

Exit the program. Bye!

这些数字是我输入的。我用谷歌搜索了一下，认为这是因为缓冲区的原因。所以我尝试在写入之后添加刷新(stdout)或刷新(输出)。但效果还是不太好。

我希望它的工作原理是:

Please input the express: 123
The expression is: 123
Please input the express: 234
The expression is: 234
Please input the express: 345
The expression is: 345

Exit the program. Bye!

谢谢!对不起我的傻瓜~

<小时/>

补充:我尝试过(谢谢你，Aloush!)

Program main;
var invalue:string;
Begin
        (*Until the EOF, this loop continue to work*)
        while not eof do
        begin
                Write('Please input the express: ');
                Flush(StdOut);
                Readln(invalue);
                Writeln('')
                Writeln('The expression is: ',invalue);
        end;
        Writeln('');
        Writeln('Exit the program. Bye!');
End.

结果仍然不太好:

1
Please input the express: 
The expression is: 1
2
Please input the express: 
The expression is: 2
3
Please input the express: 
The expression is: 3
4
Please input the express: 
The expression is: 4
5
Please input the express: 
The expression is: 5

Exit the program. Bye!

Readln 仍然在第一次 Write 之前执行。

顺便说一句，我也尝试过:

Program main;
var invalue:string;
Begin
        (*Until the EOF, this loop continue to work
        while not eof do
        begin*)
        Repeat
                Write('Please input the express: ');
                Flush(StdOut);
                Readln(invalue);
                Writeln('The expression is: ',invalue);
        Until eof;
        Writeln('');
        Writeln('Exit the program. Bye!');
End.

在这种情况下，第一个循环是好的，但其他循环仍然是错误的。

Please input the express: 123
The expression is: 123
234
Please input the express: The expression is: 234
345
Please input the express: The expression is: 345

Exit the program. Bye!

谢谢!

<小时/>

最终解决方案: http://www.amath.unc.edu/sysadmin/DOC4.0/pascal/lang_ref/ref_io.doc.html#592这是因为，eof实际上对应的是隐式读取。当前的代码应该是:

Program main;
var invalue:string;
Begin
        (*Until the EOF, this loop continue to work*)
        Write('Please input the express: ');
        while not Eof  do
        begin
                Readln(invalue);
                Writeln('The expression is: ',invalue);
                Write('Please input the express: ');
        end;
        Writeln('');
        Writeln('Exit the program. Bye!');
End.

最后，谢谢这里的Aloush和CSDN上的kei!

Answer 1

你能尝试以下方法吗？

Program main;
var invalue:string;
Begin
        (*Until the EOF, this loop continue to work*)
        while not eof do
        begin
                Write('Please input the express: ');
                Flush(StdOut);
                Readln(invalue);
                Writeln('')
                Writeln('The expression is: ',invalue);
        end;
        Writeln('');
        Writeln('Exit the program. Bye!');
End.