I/O Stream String Manipulation (Correct Cin/cout operators <>)

Question

I came across this question on here and had a further question about the answer give (I can't comment since I'm new to stackoverflow). The guy who answered it seems to be right about replacing << >> for cin and cout. But the problem I'm having is that all the semi-colons won't show up in the new output file.

I know that while std::getline(input, command, ';') erases all semicolons, but theyre supposed to be put back with the else statement at the end, but it isn't being replaced when I run it. And if I omit ';' out of the getline statement everything in the output file messes up.

How do you make it show that the semi-colon does show?

void print(ifstream& input,ofstream& output)
{
    bool first = true;
    std::string command;
    while(std::getline(input, command, ';'))
    { // loop until no more input to read or input fails to be read
        if (command.find("cin")!= std::string::npos)
        { // found cin somewhere in command. This is too crude to work. See below
            size_t pos = command.find("<<"); // look for the first <<
            while (pos != std::string::npos)
            { // keep replacing and looking until end of string
                command.replace(pos, 2, ">>"); // replace with >>
                pos = command.find("<<", pos); // look for another 
            }
        }
        else if (command.find("cout")!= std::string::npos)
        { // same as above, but other way around
            size_t pos = command.find(">>"); 
            while (pos != std::string::npos)
            {
                command.replace(pos, 2, "<<");
                pos = command.find(">>", pos);
            }
        }
        if (! first)
        {
            output << command; // write string to output
        }
        else
        {
            first = false;
            output << ';' << command; // write string to output
        }
    }
}

The `std::getline` function does not alter the contents of the flle. — Thomas Matthews, Nov 04 '16 at 03:59
Please edit your question with the code you are having issues with. — Thomas Matthews, Nov 04 '16 at 04:00
Is this the actual code? The `look_for_arrow1` variable seems to be undeclared. — nomadictype, Nov 04 '16 at 05:50
edited with the code from the link. its spitting an output file with the correct text and corrected cin/cout operators but without the semicolons. i assume getline is doing this but i thought the else statement at the end is putting it back in. — Deegeeek, Nov 04 '16 at 06:01
Can confirm the problem. I've added a comment on the answer you linked. — nomadictype, Nov 04 '16 at 07:58
A good example why why one should compile and test answers. I wonder what that idiot was thinking? — user4581301, Nov 04 '16 at 15:27

score 0 · Accepted Answer · answered Nov 04 '16 at 08:03

0

The problem is here:

        if (! first)
        {
            output << command; // write string to output
        }
        else
        {
            first = false;
            output << ';' << command; // write string to output
        }

In the first iteration, the else branch gets executed and a semicolon is printed.

In any later iteration, the if branch is executed, which does not print a semicolon.

The fix is easy: Swap the two lines starting with output <<.

answered Nov 04 '16 at 08:03

nomadictype

700
4
11

Thanks you. It seems to be working now. However, a semi-colon appears now at the beginning of the txt file I was testing. All the semicolons that were omittted with getline comeback, but a new one appears as the first character in the file. – Deegeeek Nov 04 '16 at 16:56
Actually fixed it. In the `if(! flag)` statement I just added and `&& !(line.find("#") != string::npos))` – Deegeeek Nov 04 '16 at 17:07

I/O Stream String Manipulation (Correct Cin/cout operators <>)

1 Answers1

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