Can you define a function returning bool in C?

Question

I have very little experience in C or C++, so I don't understand some of the various shortcuts and common tasks in the language.

I'm looking at game code that looks similar to this:

bool
update_frame (void)
{
  // Various bits of code
  return TRUE;
}

This is the main loop of the game. I'm thinking that it's similar to something like:

while (true) {
  // do stuff
}

Which I would use in C# or Java. Is this what's going on here?

Can you please be a little clearer as to what exactly your question is? — Eugene S, Aug 13 '11 at 04:33
You need to be clearer with your question. But to answer the titular question.... Yes, you can define a function returning bool in C. — Dark Star1, Aug 14 '11 at 13:55

score 1 · Accepted Answer · answered Aug 13 '11 at 04:30

1

This code is likely using a game engine. The engine will call update_frame 30/60/X times per second. In between, however, it might perform other tasks.

It probably functions as a while(true) loop, though.

answered Aug 13 '11 at 04:30

Christian Mann

8,030
5
41
51

score 0 · Answer 2 · answered Aug 13 '11 at 04:36

0

No tricks in the function you mentioned, its just a simple function.... the loop is probably in some other function that is calling this function.

tip: try locating that calling function for better understanding.

answered Aug 13 '11 at 04:36

Umair Ahmed

11,238
5
33
39

score 0 · Answer 3 · answered Aug 13 '11 at 04:58

0

bool is just one data type just like int, float....etc

In c you can not give name of function same as any data types or keywords.

In your code i think bool is not part of your function name...it is just return type of that function

answered Aug 13 '11 at 04:58

Jeegar Patel

26,264
51
149
222

score 0 · Answer 4 · answered Aug 13 '11 at 05:05

0

Whatever is it what you're asking, I can say that your pieces of code mean absolutely the same in C, Java and C#: the first one is a function returning bool, the second one is an infinite loop.

What is the question, again?

answered Aug 13 '11 at 05:05

hamstergene

24,039
5
57
72

Your answer seems like a comment. – Saeed Aug 13 '11 at 05:11

score 0 · Answer 5 · answered Aug 13 '11 at 05:10

It is just a simple function which returns a bool value. But, as you say it was for a game, I think somewhere in the code(probably main function) it sets this function as an update function, with a command like this:

setUpdateFrameFunc(update_frame);

And after this line, it will make a thread and run this function on that thread over and over. Finally, It seems that the code on the function is running in a while(true) loop.

score 0 · Answer 6 · edited May 23 '17 at 09:59

I think (at least the title implies) that you wonder how it is possible to specify true and bool in C, yes?

ANSI C (C89/C90) does not provide a special data type for booleans; boolean functionality is expressed using integers, where 0 stands for "false" and everything else is interpreted as "true".

C99 provides "built-in support", though, by defining appropriate macros as you can see in this answer.

So, either the code you are looking at is using C99 (check whether the header is included somewhere) or bool is a typedef macro, so look out whether there's a

typedef int bool;

or something similar to be found in the code. The mere fact that it says "return TRUE" would imply the latter, since TRUE is very common in ANSI C and most often defined as

#define TRUE 1

So again you may look out for that.

As to your other question what that function might do, it could be implemented similar to a "game loop"/while(true) loop, like this:

while (update_frame()) { /* render current state to screen */
  /* do game logic */
}

Can you define a function returning bool in C?

6 Answers6