Arithmetic infix to postfix

gistfile1.txt

#include <iostream>
using namespace std;

char input[]="9+8*2/6";
char* head = input;

void expr();
void match(char ch);
void exprPrime();
void term();
void factor();

int main(){
    expr();
}

void expr(){
    term();
    exprPrime();
}

void match(char ch){
    if (ch == *head){
        head++;
    }
}

void exprPrime(){
    if (*head == '+'){
        match('+');
        term();
        cout << "+";
        exprPrime();
    }
    else if (*head == '-'){
        match('-');
        term();
        cout << "-";
        exprPrime();
    }
    else{
        term();
    }
}

void term(){

    if (*head=='*'){
        match('*');
        factor();
        cout << "*";
        term();
    }
    else if (*head=='/'){
        match('/');
        factor();
        cout << "/";
        term();
    }
    else{
        factor();
    }
}

void factor(){
    if ( isdigit(*head)){
        cout << *head;
        head++;
    }
}