cpp run function that before it is declared? - c++

Question

I'm new to CPP, and I want to know how to run a function that isn't in its scope. I'm used to doing such things in javascript, and I get an error CPP when I try to do that. What I mean is the below:
#include <iostream>
using namespace std;
int tic_h;
int tic_v;
void echo(string e_val){
cout << e_val;
}
void c_mes(){
echo("X|0|X\n");
echo("-----\n");
echo("X|0|X\n");
echo("-----\n");
echo("X|0|X\n");
s_v();
}
void s_v(){
echo("Please enter vertical coordinate: ");
cin >> tic_v;
if(tic_v<4&&tic_v>0){
c_mes();
}else{
s_v();
}
}
void s_h(){
echo("Please enter horizontal coordinate: ");
cin >> tic_h;
if(tic_h<4&&tic_h>0){
s_v();
}else{
s_h();
}
}
int main(){
s_h();
return 0;
}
I get this error:
error: 'sv' was not declared in this scope on line 16
How can I make it work?

Answer 1

You should put a function prototype before using the function, for the compiler to know what it is going to be.
Put
void s_v(); // prototype your functions, this is usually done in include files
Right after the #include line.

Answer 2

You'll need to forward declare dostuff, as in the example below.
By doing this you pretty much tell the compiler that the function will be defined else where, but that you'd like to use it.
Excuse the wording, but putting it the way I did is easily comprehensive by a novice programmer.
#include <iostream>
using namespace std;
void dostuff (); // forward declaration
void test(int b){
if(b<11&&b>0){
cout << "Yay!";
}
else{
cout << "The number is not between 1 and 10.";
dostuff();
}
}
void dostuff(){
int numput;
cout << "Please type a number between 1 and 10:";
cin >> numput;
test(numput);
}
int main(){
dostuff();
}
OP just edited the original snippet provided in his question (which the below is a modification off), I'll leave this post the way it is since it explains the situation quite well.

Answer 3

You need to add void s_v(); before the c_mes() function. This is called a function prototype, and it lets the compiler know that that symbol exists and will be implemented later in the code:
#include <iostream>
using namespace std;
int tic_h;
int tic_v;
void s_v();
void echo(string e_val) {
cout << e_val;
}
void c_mes() {
echo("X|0|X\n");
echo("-----\n");
echo("X|0|X\n");
echo("-----\n");
echo("X|0|X\n");
s_v();
}
void s_v() {
echo("Please enter vertical coordinate: ");
cin >> tic_v;
if (tic_v < 4 && tic_v > 0) {
c_mes();
} else {
s_v();
}
}
void s_h() {
echo("Please enter horizontal coordinate: ");
cin >> tic_h;
if (tic_h < 4 && tic_h > 0) {
s_v();
} else {
s_h();
}
}
int main() {
s_h();
return 0;
}
Keep in mind that if you ever change the signature for s_v() (that is, add arguments or change the return type), you will need to update the prototype as well.

Answer 4

Declare dostuff somewhere before the void test definitionm e.g on line 3:
void dostuff();
This way you introduce the signature of dostuff function to your program before the function is defined.
In C++ unlike javascript and some other languages, the parser doesn't find all functions then compile the code.

Answer 5

add
void dostuff();
just after the using namespace std; and it will work :)

Answer 6

This is the same error, you use a function before declare it (s_v()), for solve your error you only should create a prototype of s_v():
void s_v(); //at the start of your file

Answer 7

write this
void c_mes(){
echo("X|0|X\n");
echo("-----\n");
echo("X|0|X\n");
echo("-----\n");
echo("X|0|X\n");
s_v();
}
after this
void s_h(){
echo("Please enter horizontal coordinate: ");
cin >> tic_h;
if(tic_h<4&&tic_h>0){
s_v();
}else{
s_h();
}
}