c++ combine erase and remove string

Question

I saw someone use this line to remove white spaces from string stored in a vector, but I fail to understand the reason for using erase and remove this way? The second question: how can I, instead of only removing white spaces, remove anything that is not a 'num' or a '-' ?

this is not the full code, it is only a snippet, will not compile. the vector simply contains raw strings of a text file, the strings were comma delimited, currently the strings could contain any possible char except the comma.

vector <string> vecS;
ifstream vecStream;
while(vecStream.good()) {
 vecS.resize(i+1);
 getline(vecStream, vecS.at(i), ',');
 vector <string> vecS;          
 vecS.at(i).erase(remove( vecS.at(i).begin(), vecS.at(i).end(), ' '), vecS.at(i).end());
 i++
}

EDIT; added more code, hope this is clearer now

Did you know you can format code as code? When you edit your question, look for the orange ? It will give you some help (you can also hover over the other buttons too). — crashmstr, Jun 04 '14 at 12:34
Please post **real code**. The current code won't compile. With hypothetical code guessing at the rationale of the real code that served as inspiration, becomes … a guessing game. — Cheers and hth. - Alf, Jun 04 '14 at 12:36
@Samuel yeah i edited my question and lost the code formatting, you were faster than me to fix it — Molegrammer, Jun 04 '14 at 12:36
-1: Not real code, not valid syntax, what on earth is that `ifstream` doing there?! — Lightness Races in Orbit, Jun 04 '14 at 12:41

Columbo · Accepted Answer · 2014-06-04T12:49:17.553

1

but I fail to understand the reason for using erase and remove this way?

std::remove basically rearranges the sequence so that the elements which are not to be removed are all shifted to the beginning of the sequence - a past-the-end iterator for that part, and effectively the new end of the sequence, is then returned.

There is absolutely no need for a file stream in that snippet though:

vector <string> vecS;
// Do something with vecS

for( auto& s : vecS )   
    s.erase( remove_if( std::begin(s), std::end(s), 
                        [](char c){ return std::isspace(c); }), // Use isspace instead, that recognizes all white spaces
             std::end(s) );

edited Jun 04 '14 at 12:49

answered Jun 04 '14 at 12:39

Columbo

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thanks :) how can extend this to remove everything that is not a number or a '-' ? – Molegrammer Jun 04 '14 at 12:46
@Molegrammer In the lambda, instead of just using `isspace`, add the appropriate conditions. – Columbo Jun 04 '14 at 12:52
@Molegrammer So the condition is `!std::isdigit(c) && c != '-'` – Columbo Jun 04 '14 at 12:53
would this also remove white spaces ? – Molegrammer Jun 04 '14 at 13:19

c++ combine erase and remove string

1 Answers1