c++ boost split string

Question

I'm using the boost::split method to split a string as this:

I first make sure to include the correct header to have access to boost::split:

#include <boost/algorithm/string.hpp>

then:

vector<string> strs;
boost::split(strs,line,boost::is_any_of("\t"));

and the line is like

"test   test2   test3"

This is how I consume the result string vector:

void printstrs(vector<string> strs)
{
    for(vector<string>::iterator it = strs.begin();it!=strs.end();++it)
    {
        cout << *it << "-------";
    }

    cout << endl;
}

But why in the result strs I only get "test2" and "test3", shouldn't be "test", "test2" and "test3", there are \t (tab) in the string.

Updated Apr 24th, 2011: It seemed after I changed one line of code at printstrs I can see the first string. I changed

cout << *it << "-------";

to

cout << *it << endl;

And it seemed "-------" covered the first string somehow.

Show how you work with the vector. I'd guess the issue is there. — Nikolai Fetissov, Apr 20 '11 at 17:44
`boost::is_any_of("\t")` is less efficient then `[](char c) { return c=='\t';}`. You just want to check a single possibility. (No idea why there's no `boost:is('\t')` ) — MSalters, Aug 26 '13 at 10:33
What does the code in @MSalters comment mean? How do I use that code to substitute `boost::is_any_of()`? — Posco Grubb, Aug 05 '16 at 18:22
@PoscoGrubb: It's called a "lambda", and `boost::splits` understands them. — MSalters, Aug 06 '16 at 17:28

score 92 · Accepted Answer · edited May 12 '23 at 20:35

92

The problem is somewhere else in your code, because this works:

string line("test\ttest2\ttest3");
vector<string> strs;
boost::split(strs,line,boost::is_any_of("\t"));

cout << "* size of the vector: " << strs.size() << endl;    
for (size_t i = 0; i < strs.size(); i++)
    cout << strs[i] << endl;

and testing your approach, which uses a vector iterator also works:

string line("test\ttest2\ttest3");
vector<string> strs;
boost::split(strs,line,boost::is_any_of("\t"));

cout << "* size of the vector: " << strs.size() << endl;
for (vector<string>::iterator it = strs.begin(); it != strs.end(); ++it)
{
    cout << *it << endl;
}

Again, your problem is somewhere else. Maybe what you think is a \t character on the string, isn't. I would fill the code with debugs, starting by monitoring the insertions on the vector to make sure everything is being inserted the way its supposed to be.

Output:

* size of the vector: 3
test
test2
test3

edited May 12 '23 at 20:35

yano

4,827
2
23
35

answered Apr 20 '11 at 17:50

karlphillip

92,053
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426

2

There's nothing else we can do for you if you won't share a minimal example that reproduces the problem you are facing. Remember: MINIMAL EXAMPLE, not your full app. – karlphillip Apr 20 '11 at 18:21
thanks. it seemed I changed cout<<*it<< "-------" to cout<<*it< – icn Apr 25 '11 at 04:39
6

FYI, following Boost headers are used in this sample: `#include ` and `#include ` – Richard Dally Jan 20 '16 at 09:07
This does not work. Try string = "hih1ihi" and substring = "hi. The result of the work is incorrect. – Optimus1 Nov 17 '21 at 14:47

score 15 · Answer 2 · answered Aug 28 '12 at 16:14

My best guess at why you had problems with the ----- covering your first result is that you actually read the input line from a file. That line probably had a \r on the end so you ended up with something like this:

-----------test2-------test3

What happened is the machine actually printed this:

test-------test2-------test3\r-------

That means, because of the carriage return at the end of test3, that the dashes after test3 were printed over the top of the first word (and a few of the existing dashes between test and test2 but you wouldn't notice that because they were already dashes).

score 3 · Answer 3 · answered Apr 09 '21 at 13:44

template <class Container>
void split1(const std::string& str, Container& cont)
{
   boost::algorithm::split_regex(cont, str, boost::regex("\t"));
}

std::vector<std::string> vec1;
std::string str = "hest1\twest2\tpiest3";
split1(str, vec1);

vec == ("hest1","west2","piest3")

c++ boost split string

3 Answers3

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