OpenEuphoria

1. Hard to find bug in my app

• Posted by justaguy Nov 08, 2009
• 964 views

Short version:

Function calls don't actually *require* you to receive the returned value. Is this expected and intended behavior? It resulted in a hard to find logic error for this newbie.

• • • • • • • long boring version with background info and example code

I'm a casual programmer, decided I was going to relearn Eu, and was excited to find OpenEu was moving to 4.0. So I installed it, and downloaded a few things I thought looked interesting, one of which includes Raymond Smith's EuAllegro wrappers.

Was playing with one of his examples, decided to comment it to figure out how it worked. While doing that, I also decided to change some stuff that I thought should be organized differently. One of them was a collision check outside of the collision check function call. He had 3 collision checks, one for the left, one for the right, and one for straight ahead. The one for straight ahead was out of the collision check function.

So I moved the straight ahead collision check to the proper function, and replaced his old code with a call to the function. But the app no longer registered those collisions, although it registered the left and right collisions.

Tried to track the error down over a couple of days. Last night finally figured it out. I was returning a value to the function, but my call to that function did not have a variable to receive the returned value. For example:

function colcheck() fin = TRUE end function

... some stuff colcheck()

if fin = TRUE then exit() end if

3. Re: Hard to find bug in my app

• Posted by justaguy Nov 10, 2009
• 877 views

function colcheck() 
    fin = TRUE 
end function 
 
... some stuff 
colcheck() 
 
if fin = TRUE then exit() end if 

Your example code contradicts your statement. In your example code, colcheck() does not return a value from the function. That should not work and if it ran, that is a bug.

However, functions can return values but the caller is not required to retrieve the value returned by the function. It can ignore the return value.

[/quote]

Yes, sorry, I got interrupted while I was typing it in.

I tried

function colcheck() 
    fin = TRUE 
end function 
 
... some stuff 
colcheck() 
 
if fin = TRUE then exit() end if 

and the interpreter gave me an error.

when I changed

fin = TRUE 

to

fin = TRUE 
return fin 

The interpreter was happy.

I suspected nothing required you to actually assign the return value, but wasn't sure.

Thanks.