May I ask why this works:

given:
char s[];
char *posbfr = s;
char *endbfr = s + MAXOP;

void(...){
if (posbfr >= endbfr)
	printf("......");
	else
    *posbfr++ = c ;
}


but this is invalid?

(posbfr >= endbfr) ? printf("......") : *posbfr++ = c ;

(with an "invalid lvalue in assignment") error?

or...is this the dumbest question yet? :-)

Thank you.

mdh wrote:
> May I ask why this works:
> 
> given:
> char s[];
> char *posbfr = s;
> char *endbfr = s + MAXOP;
> 
> void(...){
> if (posbfr >= endbfr)
> 	printf("......");
> 	else
>     *posbfr++ = c ;
> }
> 
> 
> but this is invalid?
> 
> (posbfr >= endbfr) ? printf("......") : *posbfr++ = c ;
> 
You are assigning c to the result of the conditional expression, so the
above equivalent to

((posbfr >= endbfr) ? printf("......") : *posbfr++) = c ;

-- 
Ian Collins.

mdh wrote:

> May I ask why this works:
<snip>
> but this is invalid?
> 
> (posbfr >= endbfr) ? printf("......") : *posbfr++ = c ;
> 
> (with an "invalid lvalue in assignment") error?

Assignment is lower priority than ?:. The compiler sees your expression 
as (cond ? x : y) = c;

Try explicit parentheses, like this:

(posbfr >= endbfr) ? printf("......") : (*posbfr++ = c) ;

On Oct 28, 4:02 pm, Ian Collins <ian-n...@hotmail.com> wrote:
> mdh wrote:
>
> > but this is invalid?
>
> > (posbfr >= endbfr) ? printf("......") : *posbfr++ = c ;
>

> Ian Collins wrote:

> You are assigning c to the result of the conditional expression, so the
> above equivalent to
>
> ((posbfr >= endbfr) ? printf("......") : *posbfr++) = c ;
>



Ian,
I know I am not then understanding this. I thought, given

expr1 ? expr2 : expr3;

then, if expr1 evaluates to true, then expr2 is evaluated, else if
false, expr3.

So, in the above case, is an assignment not regarded as a valid
expression?
..

On Oct 28, 4:03 pm, Peter Pichler <use...@pichler.co.uk> wrote:
> mdh wrote:
> > May I ask why this works:
>
>
> Try explicit parentheses, like this:
>
> (posbfr >= endbfr) ? printf("......") : (*posbfr++ = c) ;

Aha...thank you.