Thread: Can you make an array of commands?

Hello,

I hope you are having a good day and thank you for your time.

Is it possible to make an array of commands such that if I want to go to a function with a certain input, I can use the input as an offset which will access a certain command and then return?
(some of this is pseudo code, so I left out the ;'s)

Code:

array1[7] = {command1,command2,command3,...,command7}
int main(void)
{
//do some stuff
get input from keyboard
n = keyboard input //pseudo code
array1[n]  //Can I do this?
}

Can I just write an array of commands like this?:

Code:

cmdarray1[10] = {PlaySnd(6), SysBeep(200), SendString("Hello"),....., DelaySecs(4)}

and access it like this?:
i = keyboard input //pseudo code
cmdarray1[i];

Thanks.

You can make an array of function pointers, but not of function calls (with the parentheses already filled in).

[SIZE=1][SIZE=1]

Originally Posted by tabstop

You can make an array of function pointers, but not of function calls (with the parentheses already filled in).

So I looked at the "Array of Function pointers" stuff and it looks really helpful.

So I made my array:

Code:

int (*FunArray1[8]); 
	FunArray1[0]=playPT1;
	FunArray1[1]=playPT2;
	FunArray1[2]=playPT3;
	FunArray1[3]=playPT4;
	FunArray1[4]=playPT5;
	FunArray1[5]=playPT6;
	FunArray1[6]=playPT7;
	FunArray1[7]=playPT8;

and in my program, I do this:

Code:

if((the user did something))
{
	while(funIndex<=8) //don't want to go above the index
	{
	*FunArray1[funIndex];   //assume funIndex=0
	}
}
void playPT1(void)
{
	
	PlaySnd();//this works fine, I just took out the variables for simplicity
        funIndex++;
	return funIndex;
}

Error message:
type mismatch, expected 'int (*)(int)', found 'void (*)(void)'

Thank you for your help!!!

All I really want to do is go to the function and do something then return nothing.

A 2d array could be used to store the arguments.

Or you could make life a whole lot simpler and just use a switch() statement to call functions based on your keyboard input.

Originally Posted by AndrewHunter

There you go trying to make things simple again Tater.

As for the OP, Tater's point really is the simpliest and best solution for what it appears you want to do. However, if you want to go the function pointer route, for academia I suppose, here is a quick example:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void  myHello(void);
void  myGoodBye(void);

int main(void){

	//create framework for function table
	struct myFunctionTable{
		char *myName;
		void (*myFunction)(void);
	};

	//make function table, aka array
	myFunctionTable FunctionTable[]={{"Hello", &myHello}, {"GoodBye", &myGoodBye}};

	char myAnswer[10];


	printf("Which function to run?");
	scanf("%s", myAnswer);

	//find and run function
	for(int i = 0; i < (sizeof(FunctionTable) / sizeof(myFunctionTable));i++){
		if(strcmp(FunctionTable[i].myName,myAnswer)==0){
			FunctionTable[i].myFunction ();
			break;
		}
	}
	getchar();
	getchar();
	return (0);
}
//Implement functions
void myHello(void){
	printf("Hello World\n");
}
void myGoodBye(void){
	printf("GoodBye World\n");
}

Are you sure that

Code:

myFunctionTable FunctionTable[]={{"Hello", &myHello}, {"GoodBye", &myGoodBye}};

is correct syntax?

Originally Posted by ☼Aulos

Are you sure that

Code:

myFunctionTable FunctionTable[]={{"Hello", &myHello}, {"GoodBye", &myGoodBye}};

is correct syntax?

Is there a reason you believe it isn't? (For example, if you tried it and the compiler complained, then that would be a reason that presumably you would tell us about.)

In fact, it is almost but not quite right syntax, as the word "struct" needs to be right before it.

So you'll have to decide what type of things you want: do you want functions that take an int and return an int (which is "int (*)(int)"), or that take no arguments and return nothing (which is "void (*)(void)")? They aren't compatible with each other.

You should also get at least a warning for trying to return funIndex from a void function.

Here's what your declaration of FunArray looks like to the compiler. Note, I added the parentheses in purple that you seem to have forgotten, or that the compiler filled in for you.

Code:

int (*FunArray1[8])(int);

FunArray is an array of 8 pointers to functions that take an int and return an int.

Here is the declaration of playPT1 you try to assign to your array:

Code:

void playPT1(void)

playPT1 is a function that takes nothing and returns nothing.

Notice how the purple and red parts don't match up between the two? For proper assignment, function pointers have to match parameter count and types as well as return type. You either need to make FunArray void-void:

Code:

void (*FunArray1[8])(void);

or make your playPT functions int-int:

Code:

int playPT1(int x)

Originally Posted by anduril462

Here's what your declaration of FunArray looks like to the compiler. Note, I added the parentheses in purple that you seem to have forgotten, or that the compiler filled in for you.

Code:

int (*FunArray1[8])(int);

FunArray is an array of 8 pointers to functions that take an int and return an int.

Here is the declaration of playPT1 you try to assign to your array:

Code:

void playPT1(void)

playPT1 is a function that takes nothing and returns nothing.

Notice how the purple and red parts don't match up between the two? For proper assignment, function pointers have to match parameter count and types as well as return type. You either need to make FunArray void-void:

Code:

void (*FunArray1[8])(void);

or make your playPT functions int-int:

Code:

int playPT1(int x)

Does it matter whether the functions that the array is pointing to return or take values? I wouldn't think so, so I made the the functions void-void.

What does the input to the functions have to do with its index on the array?

I thought "int (*FunArray1[8])(int);" took a value (funIndex) and returns an address, the the program goes to the function and when I type in "return;", it goes back to the main program? Am I wrong? ( I realize I probably am wrong about everything I've said).


Can I use the int "int (*FunArray1[8])(int funIndex);" (its declaration) like this:

*FunArray1[funIndex];

to go to the function I want, then, in the function put "return;" to go back to the main program?

So I guess this is where I am confused especially, why do I have to declare the array like this:
int (*FunArray1[8])(int funIndex);

When I am passing a parameter into the array (funIndex) within the []'s?

Could I declare the function like this:
int (*FunArray1[int funIndex = 8]; since the []'s is where I am passing the index right?