Little C++ Question

EsX_Raptor

United States2801 Posts

November 12 2008 18:00 GMT

Assume I have a file with this content:

a b c d
e f g h i
j k l

and I have a char variable a:

char a;

Now suppose I read each letter and do something with it, such as converting it to a number. The desired output in a new file should be:

1 2 3 4
5 6 7 8 9
10 11 12

Don't pay attention to the numbers, but rather the format of the output (3 lines).

My problem is: I don't know how to read the newline character correctly. I've already tried

File >> a;
if (a == '\n')
Out << '\n';

That would create a new line in the output file. But for some reason it just doesnt work and the output is the following:

1 2 3 4 5 6 7 8 9 10 11 12

No formatting. Anyone has suggestions on how to create that newline?

EsX_Raptor

United States2801 Posts

November 12 2008 18:09 GMT

Apparently the newline character '\n' cannot be read by the char variable a and thus the "if" isn't executed. -.-

dyodyo

Philippines578 Posts

November 12 2008 18:10 GMT

edit
+ Show Spoiler +

Try this and see if it works...
Try viewing the file in a hex editor to see if the newline character is correctly inserted in the file (ascii code 10). You can also try viewing the file in wordpad. Note that windows uses the \r\n combination as line endings. So if you just insert \n and open the file in notepad, it wont have multiple lines (but you would see a block character where the \n characters are located.

nice to see you figured it out

freelander

Hungary4707 Posts

November 12 2008 18:15 GMT

>> operator doesn't read whitespace characters such space, /n , tab I think.
You should use the std function getline(i instream, string s), it reads a whole a line from an instream and writes to string s.

EsX_Raptor

United States2801 Posts

November 12 2008 18:21 GMT

But my program is designed to read each input in the file one at a time and perform some operation on them.

And as you said, >> operator doesn't read whitespaces nor '\n' symbol.

if I add, say a letter 'x' at the end of each line and go:

if (a == 'x')
Out << '\n';

it works fine -.-

freelander

Hungary4707 Posts

November 12 2008 18:29 GMT

On November 13 2008 03:21 EsX_Raptor wrote:
But my program is designed to read each input in the file one at a time and perform some operation on them.

And as you said, >> operator doesn't read whitespaces nor '\n' symbol.

if I add, say a letter 'x' at the end of each line and go:

if (a == 'x')
Out << '\n';

it works fine -.-

ok.. but adding an additional x sounds silly because if you have to work with files like this(for example ini files) you should use the getline.
if you read a line into a string var, you can see what was the last character in that line.
If you know this, you can add a /n after converting the said letter to number.

MasterZilla

Sweden234 Posts

November 12 2008 18:30 GMT

You can open the stream with the 'noskipws' flag, which allows you to read whitespace.

As for the line breaking, use Out << endl; in stead.

freelander

Hungary4707 Posts

November 12 2008 18:34 GMT

On November 13 2008 03:30 MasterZilla wrote:
You can open the stream with the 'noskipws' flag, which allows you to read whitespace.

As for the line breaking, use Out << endl; in stead.

hey, how should this be done?

ifstream f("fname.txt");

where to put this flag?