i get this error:C:\Users\Owner\MadV\main.cpp|873|undefined reference to `BigNum::operator++(int)'|

when i try to use functions from my BigNum.c files, the functions have been declared in BigNum.h, these are my main.cpp includes:

include <cmath>
include <stack>
include<queue>
include <iostream>
include <ranges>
include <regex>
include <vector>
include <thread>
include <bitset>
include <ctime>
include <iterator>
include <math.h>
include <bits/stdc++.h>
include "vytecode.h"
include "debugger.h"
include "vytemachine.h"
include "BigNum.h" // never incude .c/cpp files
include <time.h>
define M_PI 3.141592653589793
include<windows.h>
include <SFML/Graphics.hpp>
include <map>
include <chrono>
include <GL/gl.h>
include <string>
define gkey GetAsyncKeyState
define rxs regex_search
define rxp regex_replace
define rxm regex_match
define icas std::regex_constants::icase
include <immintrin.h>

is there any thing causing this in the guards? in the BigNum.h file i have pragma once, so i don't think that should be causing any errors.

definition of functions in my BigNum class( in BigNum.h):

inline BigNum operator+( BigNum &other) ;

inline BigNum operator-( BigNum &other) ; // dont change to * bc its slower

inline BigNum operator*( BigNum other) ;

inline BigNum operator/( BigNum other) ;

inline void operator++(int);

inline void operator--(int);

inline bool operator>(const BigNum& other) const;

inline bool operator<(const BigNum& other) const;

inline bool operator>=(const BigNum& other) const;

inline bool operator<=(const BigNum& other) const;

inline bool operator==(const BigNum& other) const;

inline bool operator!=(const BigNum& other) const;

code that fails to compile(main.cpp):

BigNum test("1");

BigNum c ("32.5");

BigNum f("1.5");

double c2 = 5.2433423412;

int k2 = 10;

int f2;

testBool* x2;

x2 = new testBool[10000000];

auto t1 = std::chrono::high_resolution_clock::now();

for(auto i = 0; i<= 1e+7;i++)

{

c+f;

}

auto t2 = std::chrono::high_resolution_clock::now();

auto duration = std::chrono::duration_cast<std::chrono::milliseconds>( t2 - t1 ).count();

print(c,0);

setInt(c);

print(c,0);

std::cout<<"object: "<<duration<<std::endl;

return 0;