cin>>
the input: 0.23
Why the value of
How can I do to set the
I need the value to indicate the position where error occurs
ps: I am doing a expression parser, and I need the pos to tell the user where is the error.
For example:
the input:
>sin(3
output should be:
but now it always be like this:
|
|
Why the value of
pos is -1?How can I do to set the
pos be the value I want, I mean 4.I need the value to indicate the position where error occurs
ps: I am doing a expression parser, and I need the pos to tell the user where is the error.
For example:
the input:
>sin(3
output should be:
>sin(3
^
Error: ) is expected |
but now it always be like this:
>sin(3 ^ Error: ) is expected |
If you are writing a lexer, you can keep track of the number of characters entered in the current line
http://www.cplusplus.com/reference/iostream/istream/tellg/ :
http://www.cplusplus.com/reference/iostream/istream/tellg/ :
| Return Value An integral value of type streampos with the number of characters between the beginning of the input sequence and the current position. Failure is indicated by returning a value of -1. |
On Windows, tell/seek don't apply to stdin. I can't think of a good reason why this is the case. It could be generally true, but I don't know.
You get the same result at any level, C++, C buffered or unbuffered io, or direct os calls.
You get the same result at any level, C++, C buffered or unbuffered io, or direct os calls.
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