How to pass a local variable to another function? - c

Question

So I am doing a text adventure game. It has Hundreds of lines of story, a fully functioning combat system, and I am now trying to create an influence system. Basically it is supposed to work like this: Certain responses/actions will increase or decrease your influence over different characters. I want to use the influence variable in choice_6() and story_7(). How do I do that? Please do not send me any links. I've gone through many many other answers and they haven't made sense to me so if your going to copy and paste, at least explain it a different way than other answers. Thank you.
int choice_6()
{
int influence = 0;
int choice = 0;
printf("What do you do?\n");
printf("\t1. You: No. I know absolutely nothing about you. You could be a monster\n");
printf("\ttoo for all I know! Normal people don't turn into frogs!\n");
printf("\t2. You: Your right we should keep moving. You can tell me when your\n");
printf("\tready.\n");
printf("\t3. You: Okay where do you think should we go then?\n");
do
{
scanf_s("%i", &choice);
switch (choice)
{
case 1:
{
printf("\tBrie flashes a pained look on her face and you immediately regret saying that.\n");
printf("\tBrie: You really think I'm a monster?\n");
system("pause");
influence -= 10;
printf("You lose influence and are now at %i with Brie.\n", influence);
system("pause");
printf("Influence affects characters reactions towards you, their combat effectiveness, and even their allegiances in rare cases.\n");
printf("However, depending on the situation, low influence is not always a bad thing...\n");
system("pause");
printf("\tYou: Your right we should keep moving.\n");
break;
}
case 2:
{
printf("\tBrie: Thank you. I'd rather not discuss this my life story in a dark\n");
printf("\tdungeon.\n");
system("pause");
influence += 10;
printf("You gain influence and are now at %i influence with Brie.\n", influence);
system("pause");
printf("Influence affects characters reactions towards you, their combat effectiveness, and even their allegiances in rare cases.\n");
printf("However, depending on the situation, low influence is not always a bad thing...\n");
system("pause");
printf("\tYou: I'd have to agree with you there. Let's see what is up these stairs.\n");
choice = 2;
break;
}
case 3:
{
printf("Brie smiles at this.\n");
printf("\tBrie: Well the only way out seems to be these stairs so let's go up.\n");
system("pause");
influence += 10;
printf("You gain influence and are now at %i influence with Brie.\n", influence);
system("pause");
printf("Influence affects characters reactions towards you, their effectiveness in combat, and even their allegiances in rare cases.\n");
printf("However, depending on the situation, low influence is not always a bad thing...\n");
system("pause");
printf("\tYou: Sounds good to me I am quite frankly done with dungeons about now.\n");
break;
}
default:
{
printf("Type the number for the choice you want to do\n");
system("pause");
break;
}
}
}while(choice != 1 && choice != 2 && choice != 3);
}
int story_7()
{
printf("\ninfluence is %i\n", influence);
printf("You lead the way walking upstairs\n");
system("pause");
printf("You turn the corner while crouched to find a room full of gremlins and goblins.\n");
system("pause");
printf("You grab Brie's hand and roll to the left behind some crates before they see you.\n");
system("pause");
printf("Even though you realize you will probably not make it out of this situation\n");
printf("alive, you can't help but feel lucky with Brie being so tightly pressed against you on the floor.\n");
system("pause");
printf("After a long period of silence to confirm nobody has seen you both enter,\n");
printf("Brie looks up at you and rolls her eyes.\n");
system("pause");
printf("*whispers*\tBrie: At least buy me dinner first jeez.\n");
system("pause");
printf("*whispers*\tYou: I'd love to but we should probably kill these uglies first.\n");
system("pause");
if (influence > 0)
{
printf("Brie laughs at this and slowly leans you off her to have both of you crouch.");
system("pause");
}
else
{
printf("Brie: Ugh just get off of me!\n");
printf("Brie pushes you off her violently and you manage to stay crouched.");
system("pause");
}
}
int main()
{
int play = 0;
int influence = 0;
intro_1();
story_1();
choice_1();
story_2();
choice_2();
story_3();
choice_3();
story_4();
choice_4();
story_5();
choice_5();
intro_2();
combat_1();
story_6();
choice_6();
story_7();
choice_7();
system("pause");
}

Answer 1

You can pass a pointer to the influence variable, if you want to modify it from within a function. Like this:
int choice_6(int *influence)
{
// ...
*influence -= 10;
// use *influence wherever you would have had used influence before
// ...
}
int story_7(int influence)
{
// ...
if (influence > 0) ...
// ...
}
int main()
{
int influence = 0;
// ...
choice_6(&influence);
story_7(influence);
// ...
}
This is passing a pointer to choice_6() because you need to modify influence from within that function. This is passing the value to story_7() because you do not need to modify the influence value there.

Answer 2

You should create game object(s) that stores the state of the game, in this case, influence and other event flags.
You will then need to either set this game object as a global, or pass it around by pointer/reference to every functions that may need to check or modify the game state.
struct MyGame {
int influence;
int has_cheese;
};
void choice_6(struct MyGame * game) {
...
game->influence += 10;
...
}
int main(...) {
struct MyGame game;
game->influence = 0;
game->has_cheese = FALSE; // or 0
...
choice_6(&game);
....
}

Answer 3

You need to pass the influence variable by reference. This means the function(s) you give the reference to can change the value of the variable itself (not just a copy of the variable).
Do this by prepending the parameter with a * in the function signatures, and passing with a & prepended:
int choice_6(int *influence)
{
....
int main()
{
int play = 0;
int influence = 0;
choice_6(&influence);
....