cpp09 ex00: Bitcoin Exchange

[Copilot]

Implements the 42 school cpp09 Exercise 00 (Bitcoin Exchange) in a new ex00/ directory. The program btc reads a CSV price database and an input file of date | value pairs, outputting each value multiplied by the exchange rate on the closest earlier date in the DB.

Structure

• BitcoinExchange.hpp/cpp — Canonical C++98 class; uses std::map<std::string, double> as the price database (ISO-8601 string keys sort chronologically, enabling lower_bound for closest-lower-date lookup)
• main.cpp — Validates argc, loads data.csv, delegates to processInput
• Makefile — Builds btc with -Wall -Wextra -Werror -std=c++98
• data.csv — Historical BTC prices 2009–2022
• input.txt — Sample input matching subject example

Key logic

Closest lower date via lower_bound:

std::map<std::string, double>::const_iterator it = _db.lower_bound(date);
if (it != _db.end() && it->first == date) return it->second; // exact
if (it == _db.begin()) throw std::runtime_error("Error: bad input => " + date);
return (--it)->second; // closest lower

Value parsing — strtod with full-string consumption check, then range/sign guards:

double value = std::strtod(valueStr.c_str(), &end);
if (end == valueStr.c_str() || *end != '\0') /* bad input */;
if (value < 0)    /* not a positive number */;
if (value > 1000) /* too large a number */;

Date validation — checks length, delimiter positions, digit-only fields, month/day bounds, and leap-year correctness for Feb 29.

Error messages (per spec)

Condition	Output
Wrong/no argument or unreadable file	Error: could not open file.
Missing | separator or bad date	Error: bad input => …
Negative value	Error: not a positive number.
Value > 1000	Error: too large a number.

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