A function was called in another previous function before creating it, terminal shows mistake

Question

In this program we play tic tac toe against AI whith minimax algorithm. This code isn't mine. Im just trying to understand why it doesn't work. Please explain why it shows mistake in function void cmp.

    #include<stdio.h>
#include<iostream>
using namespace std;
char brd[]= {49,50,51,52,53,54,55,56,57};
int mv=0;
void board() {
cout << "|_" << brd[0] << "_|_" << brd[1] << "_|_" << brd[2] << "_|\n";
cout << "|_" << brd[3] << "_|_" << brd[4] << "_|_" << brd[5] << "_|\n";
cout << "|_" << brd[6] << "_|_" << brd[7] << "_|_" << brd[8] << "_|\n\n";
}
int iswin(char le,char ar[]) {
    int cr,h,v;
    cr= ar[0]==le && ar[4]==le && ar[8]==le || ar[2]==le && ar[4]==le && ar[6]==le;
    h= ar[0]==le && ar[1]==le && ar[2]==le || ar[3]==le && ar[4]==le && ar[5]==le || ar[6]==le && ar[7]==le && ar[8]==le ;
    v= ar[0]==le && ar[3]==le && ar[6]==le || ar[1]==le && ar[4]==le && ar[7]==le || ar[2]==le && ar[5]==le && ar[8]==le ;
    return (cr||h||v); }

Here is the mistake

void cmp() {
    int bestscore=-1000,score,move,k,i;
    for(i=0; i<=8; i++) {
        if(brd[i]!='X'&& brd[i]!='O') {
            k=brd[i];
            brd[i]='O';
            score=minimax(brd,0);
            brd[i]=k;
            if(score>bestscore) {
                move=i;
                bestscore=score;
            } } }
    brd[move]='O'; }

This is function that causes mistake. It goes right after void cmp.

int minimax(char cb[],int max) {
    int i,bestscore,score,k;
    if(iswin('O',cb))
        return 100;
    if(iswin('X',cb))
        return -100;
    if(draw())
        return 0;
    if(max) {
        bestscore=-1000;
        for(i=0; i<=8; i++) {
            if(cb[i]!='X'&& cb[i]!='O') {
                k=cb[i];
                cb[i]='O';
                score=minimax(cb,0);
                cb[i]=k;
                if(score>bestscore)
                    bestscore=score;
            } }
        return bestscore; }
    else {
        bestscore=800;
        for(i=0; i<=8; i++) {
            if(brd[i]!='X'&& brd[i]!='O') {
                k=cb[i];
                cb[i]='X';
                score=minimax(cb,1);
                cb[i]=k;
                if(score<bestscore)
                    bestscore=score;
            } }
        return bestscore;
    } }

Just _declare_ the function `minimax()` before it is used. The declaration doesn't have to be a _definition_. Here is a declaration of the function: `int minimax(char[], int);` (if you want, you _can_ name the parameters but you don't have to). — Dietmar Kühl, Dec 28 '21 at 16:21
Does this answer your question? (Specifically "Use before declaration" in the first answer.) [What is an 'undeclared identifier' error and how do I fix it?](https://stackoverflow.com/questions/22197030/what-is-an-undeclared-identifier-error-and-how-do-i-fix-it) — user17732522, Dec 28 '21 at 16:27

score 1 · Answer 1 · answered Dec 28 '21 at 16:40

The compiler is clearly explaining the issue: it can't find identifier minmax. The reason it can't be found is because by the time iswin is defined minmax isn't declared. In the code minmax is declared(and defined) after it is used, thus, the compiler can't find the identifier. In order to fix it just declare it anywhere before iswin definition using:

int minimax(char cb[],int max);

You can read more about it in the following pages: microsoft, myprogrammingnotes.

If it is a matter of fundaments better grab a good book.

A function was called in another previous function before creating it, terminal shows mistake

1 Answers1