How to parse comma delimited integers from a string in c++

Question

I have a function recieving a string, which is a pair of comma delimited integers in a fashion such as "12,4". How can I parse the integers out of this string?

possible duplicate of [How to split a string?](http://stackoverflow.com/questions/236129/how-to-split-a-string) — Ed S., Apr 03 '11 at 02:44
In php you would use the `explode` function and use the comma as a delimiter. — Yzmir Ramirez, Apr 03 '11 at 02:52

score 2 · Answer 1 · answered Apr 03 '11 at 03:20

2

std::getline implements the basic "split" functionality (I don't see it mentioned in the first few answers at the other question.)

vector< int > numbers;

istringstream all_numbers_iss( "12,4" );
string number_str;
int number;

while ( getline( all_numbers_iss, number_str, ',' ) // separate at comma
        && istringstream( number_str ) >> number ) {
    numbers.push_back( number );
}

answered Apr 03 '11 at 03:20

Potatoswatter

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Shouldn't the extraction from the `istringstream` fail for passing a const as a reference for the lhs? – wilhelmtell Apr 03 '11 at 03:34
@wilhelm: No, because it is a member function. – Potatoswatter Apr 03 '11 at 03:35
It's not a `const` member. [27.6.1.2.2] – wilhelmtell Apr 03 '11 at 03:42
@wilhelm: It doesn't matter; the rvalue isn't converted to a reference. – Potatoswatter Apr 03 '11 at 04:12

score 1 · Answer 2 · answered Apr 03 '11 at 15:24

1

if you use Qt, you can use QString::split();

answered Apr 03 '11 at 15:24

shengy

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score 0 · Accepted Answer · answered Apr 03 '11 at 02:53

0

Depends whether or not you can depend on the incoming data being valid. If you can, I'd do:

#include <cstdlib>
#include <utility>
#include <string>

std::pair<int, int> split(std::string const& str)
{
    int const a = std::atoi(str.c_str());
    int const b = std::atoi(str.c_str() + str.find(',') + 1);
    return std::make_pair(a, b);
}

answered Apr 03 '11 at 02:53

ildjarn

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@rubenvb : I'm not clear what you mean by that. `atoi` is a C API and consequently cannot throw exceptions. – ildjarn Apr 03 '11 at 15:31
ok, bad wording. What I meant was that when it chokes it produces nonsense: `atoi` on a non-integer gives 0, just like `atoi` on 0 gives 0. And if the input needs validation, you might as well use the type-safe `stringstream` alternative. – rubenvb Apr 03 '11 at 16:51
@rubenvb : Which is why I specifically said "If you can (depend on the incoming data being valid)". If the data needs validation, I agree with you that `atoi` is completely inappropriate. – ildjarn Apr 03 '11 at 16:52
agreed, but it's still an awful function to use in C++. For example, see the discussion resulting from this answer: http://stackoverflow.com/questions/5017001/like-atoi-but-to-float/5017022#5017022 – rubenvb Apr 03 '11 at 16:54
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@rubenvb : Possibly, but given that I explicitly called out the caveat with using it, I don't think a downvote is warranted. Personally, I use boost.spirit.qi for this sort of thing, but I hate using it for answering trivial questions like this because it tends to raise more questions than it answers. – ildjarn Apr 03 '11 at 16:55

score 0 · Answer 4 · answered Apr 03 '11 at 02:54

0

boost tokenizer works pretty well. Click here for example.

answered Apr 03 '11 at 02:54

skimobear

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How to parse comma delimited integers from a string in c++

4 Answers4