C++ error in string replace

Question

I have created a function that replaces a string.

It looks like this:

void replace_with(wstring& src, const wstring& what, const wstring& with)
{    
    if (what != with) {
        wstring temp;
        wstring::size_type prev_pos = 0, pos = src.find(what, 0);
        while ( wstring::npos != pos ) {
            temp += wstring(src.begin() + prev_pos, src.begin() + pos) + with;
            prev_pos = pos + what.size();
            pos = src.find(what, prev_pos);
        }
        if ( !temp.empty() ) {
            src = temp + wstring(src.begin() + prev_pos, src.end());
            if (wstring::npos == with.find(what)) {
                replace_with(src, what, with);
            }
        }
    }
}

However, if my string is size==1, and the "what" is exactely the string, it will not replace it.

For example

wstring sThis=L"-";
replace_with(sThis,L"-",L"");

... will not replace the "-".

I don't see where I went wrong.

Can anybody help, please?

If this is purely a learning exercise, great, but otherwise, why aren't you using std::string::replace? — BoBTFish
– BoBTFish, Commented May 28, 2013 at 10:38

Andrey Volk · Accepted Answer · 2013-05-28 10:47:17Z

2

void replace_with(wstring &src, wstring &what, wstring &with) {
    for (size_t index = 0; ( index = src.find(what, index) ) != wstring::npos ; ) {
        src.replace(index, what.length(), with);
        index += with.length();
    }       
}

answered May 28, 2013 at 10:47

Andrey Volk

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Comments

Sebastian Redl · Accepted Answer · 2013-05-28 10:40:41Z

1

The main part of the function is working fine. The problem is the if (!temp.empty()) part, which makes absolutely no sense. Replace the entire if block with just the line

src = temp + wstring(src.begin() + prev_pos, src.end());

and it should work fine.

Hint: try to explain in words what the last part of the function is doing.

answered May 28, 2013 at 10:40

Sebastian Redl

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