Add implementation with an intentional error

CMAKE_MINIMUM_REQUIRED(VERSION 3.0)

PROJECT(factorial)

SET(CMAKE_CXX_STANDARD 11)

SET(CMAKE_CXX_FLAGS "-pedantic -Wall -Wextra")

# factorial library

ADD_LIBRARY(fact STATIC fact.c)

#include "fact.h"

unsigned long factorial(unsigned long number)

{

    unsigned long acc = 1UL;

    for (unsigned long i = 0UL; i <= number; ++i)

        acc *= i;

    return acc;

}

#ifndef FACT_H

#define FACT_H

#ifdef __cplusplus

extern "C" {

#endif // __cplusplus

unsigned long factorial(unsigned long number);

#ifdef __cplusplus

} // extern "C"

#endif // __cplusplus

#endif // FACT_H