CODEWITHSUNDEEP
c++
SeeMorton
SeeMorton

Reputation: 41

How to parse in this file in c++ dealing with spaces and new lines?

Credit 1 2 150 12345678 10-10-2020 123
Cash 2 3 199 200 1
Check 1 3 100 111000614 124356499
Credit 2 1 50 987654321 10-10-2021 321

I am trying to read in this file in c++ but I can't figure out a proper way to do it. I need to read in each individual data point into different vectors. For example in a vector called transaction type would be Credit cash check Credit.

This is the code I have now and it gives me really weird results

    file.open(fileName);
    string line;
    string space;
    while(getline(file,line,'\n')){
        cout<<"Row: ";
        while(getline(file,space,' ')){
            cout<<space<<" ";
        }
    }
    cout<<space<<" ";
    return 0;```

Upvotes: 0

Views: 661

Answers (1)

Maxim Egorushkin
Maxim Egorushkin

Reputation: 136266

Spaces and newlines are classified as (white)space in C++, see std::isspace. std::istream& operator>>(std::istream&, T&) skips all whitespace, so that no special handling for spaces or newlines is required.

One example:

#include <iostream>
#include <string>
#include <vector>

struct Date {
    unsigned yyyymmdd;
};

std::istream& operator>>(std::istream& s, Date& date) {
    std::string t;
    s >> t;
    int dd = std::stoi(t.substr(0, 2));
    int mm = std::stoi(t.substr(3, 2));
    int yyyy = std::stoi(t.substr(6, 4));
    date.yyyymmdd = yyyy * 10000 + mm * 100 + dd;
    return s;
}

struct Credit {
    int a, b, c, d, f;
    Date e;
};

std::istream& operator>>(std::istream& s, Credit& c) {
    return s >> c.a >> c.b >> c.c >> c.d >> c.e >> c.f;
}

struct Cash {
    int a, b, c, d, e;
};

std::istream& operator>>(std::istream& s, Cash& c) {
    return s >> c.a >> c.b >> c.c >> c.d >> c.e;
}

struct Check {
    int a, b, c, d, e;
};

std::istream& operator>>(std::istream& s, Check& c) {
    return s >> c.a >> c.b >> c.c >> c.d >> c.e;
}

template<class V>
void load_element(V& v, std::istream& s) {
    v.emplace_back();
    s >> v.back();
}

struct Data {
    std::vector<Credit> credits;
    std::vector<Cash> cashs;
    std::vector<Check> checks;

    Data(std::istream& s) {
        for(std::string type; s >> type;) {
            if(type == "Credit")
                load_element(credits, s);
            else if(type == "Cash")
                load_element(cashs, s);
            else if(type == "Check")
                load_element(checks, s);
            else
                throw;
        }
    }
};

int main() {
    std::istream& file = std::cin;
    Data d(file);
    std::cout << "credits: " << d.credits.size() << '\n';
    std::cout << "cashs: " << d.cashs.size() << '\n';
    std::cout << "checks: " << d.checks.size() << '\n';
}

Run it as:

./test < input.txt

input.txt contains the 4 input lines from your post.

Output:

credits: 2
cashs: 1
checks: 1

Cash in uncountable in English, however, in programming one likes to distinguish scalars and vectors/containers, hence s suffix for a vector of cash. Some of my colleagues go as far as just using suffix s for all containers regardless of arbitrary irregular rules of English, e.g. currency for scalars and currencys for vectors.

Upvotes: 2

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