🚀 go-pugleaf

In article <365@polyof.UUCP> jeff@polyof.UUCP (A1 jeff giordano ) writes:
>
>Actually I wouldn't call it a bug, but more a deficience in the
>grammar.  The following drove me nuts:
>
>		for(x=-1; x<=1; x++) { ... }
>I wanted to loop from -1 to 1.  However, the above is ambigous, it is an
>old style declaration.  I did not find out until I tried my prog on our
>UNIX system.  The UNIX cc gives:
>	Warning: oldstyle declaration on line xx.
>
>Laser gives no such warning and actually takes whatever the previous
>value was and drecrements it by one.  then does the loop.  not what i thought it
>would do.
>
>just thought I should let someone know.
>
>Goeffrey Giordano
>INET: jeff@polyof.poly.edu
>UUCP: ...!iguana!polyof!jeff
>
>Me?!? What do I know?  I'm just a brain dead poly student.


This illustrates both a blessing and a curse of the C language.  To most 
C compilers the following are equivalent:

		x -= 1;
		x =- 1;

Without the whitespace the compiler interpreted 'x=-1' to be the latter
rather than 'x=(-1)'.   Try using parens or whitespace.

This also demonstates one of the possible side-effects of macros.  The
following illustrates the point:

#define MINUS_ONE -1

x=MINUS_ONE;


...translated by the pre-processor to:

x=-1;

Again not what was intended.


To minimize the chance of these side-effects, always use parans for signed
numbers;  especially when defining them in macros (#defines).

#define MINUS_ONE (-1)

x=MINUS_ONE;

...translated by the pre-processor to:

x=(-1);


In either case the use of whitespace not only eliminates the problem but
also makes the code more readable...


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- Rick W. Frostad
- ISC Systems Corporation
- E. 22425 Appleway
- Liberty Lake, WA  99019