Can you make an array of commands?

**AndrewHunter** · 07-22-2011

You appear to be new at programming, and as such function pointers may not be the way to go with what you want to do. I posted 2 examples -- see above. The first one involves a lookup table (the one you are commenting on now) and the second one (the one I was referring to in my post) does not and is a more straighforward implementation of function pointers. I would suggest looking at that one.

Some things to note, I took the time to post 2 complete working programs for a reason - so you can copy them into your IDE and have a complete program to play with so you can start to learn how it works. By your questions it appears that you aren't doing this and thus I must have been just wasting my time.

Do me a favor, create a complete example of what you want to do. An actual program (use psuedocode where you don't know how to implement actual code). Your fun functions do not need to be fully implemented here, just give us the main body of the program. This way we can actually see what you want and then provide a way forward for you.

-Andy

**☼Aulos** · 07-22-2011

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?

**AndrewHunter** · 07-22-2011

Did you try to run the program? Does it work? Do you know what an array is or how you can implement them in C? Did you even bother to look at my other posts as I told you to? Am I the one asking for help?

**tabstop** · 07-22-2011

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.

**☼Aulos** · 07-22-2011

I apologize. My last post was put out before I saw yours starting with "You appear to be".

**AndrewHunter** · 07-22-2011

Originally Posted by tabstop

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

D*** C++ compiler foils me again.

**☼Aulos** · 07-22-2011

All,

Sorry I wasn't more clear. When I was asking questions, I was messing around with the code at the same time.

Well I tried the look up table method of function pointers and can't seem to get it to work although I though I knew how it did. For some reason, my compiler wants a ';' in front of

Code:

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

I did that and it said "illegal initialization".

I have a code that reads sections of text to the user.

Instead of just reading the sentences one after another, I would like the program to have the ability of sampling the microphone in between sections (which works fine) for "fast forward" and "repeat". The code can recognize "continue","stand by", "repeat" and "fast forward" (on the microcontroller).

I would like a section of the program with a variable "DeltaIndex" which will change values and then read the corresponding section of the text, test for "repeat" and "fast forward" again, and do it again. Here is what the code looks like:

Code:

DeltaIndex=0; // Start DeltaIndex=0 at the beginning of every text reading
if(the user said read a certain text)
{
    while(DeltaIndex<=8)  //Don't want to go past the number of sections
    {
        go to the function that reads the current section based on the index, test the mic for a word ("continue","stand by", "repeat" and "fast forward") then do that and come back here and re-evaluate the while statement then go to the function that reads the current section based on the index.
     }
}

I am currently trying to implement the suggestions above. I emphatically appreciate your help.

**☼Aulos** · 07-22-2011

So it looks like my program never actually goes to the function pointed to by DeltaIndex in the array "FunArray1":

Code:


if((the user said "watermelon"))
{
	while(DeltaIndex<=8)
	{
		_SendString232((long)"\n\r you should now go to playPT1\r\n");
		FunArray1[DeltaIndex];
	}
}

It goes in an infinite loop (which makes sense since I set DeltaIndex to 0)and prints "you should now go to playPT1" an infinite number of times and never goes into FunArray1, looks at the element with index of "DeltaIndex" and go to the function pointed to by that address, it just "skips over" FunArray1[DeltaIndex] and drops out of the program and restarts.

Code:

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

	FunArray1[0]=&playPT1;
	FunArray1[1]=&playPT2;
	FunArray1[2]=&playPT3;
	FunArray1[3]=&playPT4;
	FunArray1[4]=&playPT5;
	FunArray1[5]=&playPT6;
	FunArray1[6]=&playPT7;
	FunArray1[7]=&playPT8;
.
.
.
.

void playPT1(void)
{
	_PlaySnd(256); // this works
        DeltaIndex++;
	return;
}

Why is it just skipping over it? How do I make the program go there? I was hoping it wouldn't go in an infinite loop because I increment DeltaIndex in the playPT1 function.

I emphatically thank you for your help.

**quzah** · 07-22-2011

Code:

	while(DeltaIndex<=8)
	{
		_SendString232((long)"\n\r you should now go to playPT1\r\n");
		FunArray1[DeltaIndex];
	}

DeltaIndex[ 8 ] is out of bounds.

Quzah.

**AndrewHunter** · 07-22-2011

It is because you are not actually calling the function. Look at your code:

Code:

if((the user said "watermelon"))
{
	while(DeltaIndex<=8)
	{
		_SendString232((long)"\n\r you should now go to playPT1\r\n");
		FunArray1[DeltaIndex];
	}
}

Does anywhere in there look like a function call? All the compiler is seeing with this:

Code:

FunArray1[DeltaIndex];

is that you are listing some random memory address. In order to actually have the compiler call the function you would need something like:

Code:

if((the user said "watermelon"))
{
	while(DeltaIndex<8)
	{
		_SendString232((long)"\n\r you should now go to playPT1\r\n");
		FunArray1[DeltaIndex]();
	}
}

Note the ' () '. Now the compiler knows that you want to execute a function call. Also note I adjusted your while - loop like quzah pointed out so you wouldn't go out of bounds.

**quzah** · 07-22-2011

Of course you are still trying to access FunIndex1[ 8 ] ...

Quzah.

**AndrewHunter** · 07-22-2011

Originally Posted by ☼Aulos

I have a code that reads sections of text to the user.

Instead of just reading the sentences one after another, I would like the program to have the ability of sampling the microphone in between sections (which works fine) for "fast forward" and "repeat". The code can recognize "continue","stand by", "repeat" and "fast forward" (on the microcontroller).

I would like a section of the program with a variable "DeltaIndex" which will change values and then read the corresponding section of the text, test for "repeat" and "fast forward" again, and do it again. Here is what the code looks like:

1. How does this program get the text to read to the user?
2. Where is this text stored during program execution?
3. How did you implement "reading the text to the user" (I don't need code for txt -> audio, just where and how called)
4. How do you keep track of where the program currently is in the text?

I am asking these questions because it is starting to appear to me that something is amiss with your program design.

**AndrewHunter** · 07-22-2011

Originally Posted by quzah

Of course you are still trying to access FunIndex1[ 8 ] ...
Quzah.

Who is?

**quzah** · 07-22-2011

Originally Posted by AndrewHunter

Who is?

People in the real world? I thought I saw the = in there still.

I guess I got the top code and the bottom section confused.

Quzah.

**AndrewHunter** · 07-22-2011

Originally Posted by quzah

People in the real world? I thought I saw the = in there still.

I guess I got the top code and the bottom section confused.
Quzah.

LOL....nope, and I even gave you credit for it. Well I guess we will both have to wait until we are out of highschool to find out what happens in the real world.