C++ - lesson 4 | HackIndia Skills

C++ - lesson 4 | HackIndia Skills | HackIndia

Example

Parse simple CSV

For project data, keep the format simple. This example reads lines like item,category,amount and skips bad rows instead of crashing.

It uses getline with a comma delimiter, then converts the amount with stod inside a try block.

#include <iostream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;

struct Expense {
    string item;
    string category;
    double amount;
};

int main() {
    vector<Expense> expenses;
    string line;

    while (getline(cin, line)) {
        if (line.empty()) continue;

        stringstream ss(line);
        string item, category, amountText;

        if (!getline(ss, item, ',')) continue;
        if (!getline(ss, category, ',')) continue;
        if (!getline(ss, amountText, ',')) continue;

        try {
            double amount = stod(amountText);
            expenses.push_back({item, category, amount});
        } catch (const invalid_argument&) {
            cerr << "Skipping bad amount: " << line << '\n';
        }
    }

    double total = 0;
    for (const auto& e : expenses) total += e.amount;
    cout << "Total: " << total << '\n';
}

Tip

Ask AI carefully

You can ask ChatGPT or Gemini to generate parsing code, but give the exact input format and bad cases.

Check what it returns. Look for unchecked indexing, missing failed-read checks, and conversions that can throw without being handled.

Prompt:
Write C++17 code to read lines in this format:
item,category,amount
Skip blank lines. If amount is invalid, print an error to cerr and continue.
Do not use non-standard libraries.

Example

Sample input file

Add a small sample file to your repo. Name it something obvious, like sample_expenses.txt.

This helps another builder or internship reviewer run your project without guessing the input shape.

chai,canteen,15
bus pass,travel,450
notebook,stationery,60
wrong row,canteen,abc

Handle strings and parsing

One habit

Why parsing matters

Common input trap

Parse simple CSV

Ask AI carefully

Sample input file

Parsing checklist

Do this now

Quick check