Question

vfp关于eof、bof的问题。

go top
skip -1
?bof()
这样答案是.T.是吗？

go bottom
skip 1
?eof()
这样答案是.T.是吗？

我的意思是想问，只是go top(go bottom)是不能使?bof(?eof)为.T.的是吗？还需要skip 1(skip -1)的是吗？

Answer 1

是的，go top(go bottom)只是转到首(尾)记录，而bof()和eof()分别是测试记录指针是否在首(尾)记录的前面(后面)。所以go top(go bottom)是不能使?bof(?eof)为.T.的

Answer 2

BOF是文件头，在表的第一条记录之前，EOF是文件尾，在表的最后一条记录之后
GO TOP：把记录指针移动到第一条，GO BOTTOM：把记录指针移动到最后一条
所以：
GO TOP
? BOF() &&返回.F.
SKIP -1 &&指针往上移一条
? BOF() &&返回.T.
GO BOTTOM
? EOF() &&返回.F.
SKIP &&指针往下称一条
? EOF() &&返回.T.

Answer 3

http://msdn.microsoft.com/en-us/library/28428ed2%28v=vs.80%29.aspx
If the record pointer is positioned on the last record of a table and SKIP with no arguments is executed, RECNO( ) returns a value 1 greater than the number of records in the table and EOF( ) returns true (.T.). If the record pointer is positioned on the first record of a table and SKIP –1 is executed, RECNO( ) returns 1 and BOF( ) returns true (.T.).
[这里的大概意思是说，如果当前记录指向最后一条记录，使用不带参数的SKIP，RECNO返回记录号+1，EOF返回TRUE，如果记录指向第一条记录，SKIP -1返回记录号1，BOF返回TRUE]
http://msdn.microsoft.com/en-US/library/7yk75h22%28v=VS.80%29.aspx
GO | GOTO命令的TOP 和BOTTOM参数：
TOP
Positions the record pointer on the first record in the table. If the table has an ascending index in use, the first record is the record with the lowest key value. If the index is in descending order, the first record is the record with the highest key value.

BOTTOM

Positions the record pointer on the last record in the table. If the table has an ascending index in use, the last record is the record with the highest key value. If the index is in descending order, the last record is the record with the lowest key value.