🚀 go-pugleaf

In article <112@inesc.UUCP> jmc@inesc.UUCP (Miguel Casteleiro) writes:
>In article <36899@srcsip.UUCP>, carpent@SRC.Honeywell.COM (Todd Carpenter) writes:
>> 
>> #define SQR(x) (x*x)
>
>This macro won't work if you have SQR(a+b), because the result will be
>a+b*a+b which is diferent from what you want: (a+b)*(a+b).
>
>So, try:
>
>#define SQR(x) ((x)*(x))

Actually, this is a classic case of macro side-effect.  This also will
produce incorrect results.  Take for example the following line of C code:

	z = SQR(a++);

Now, this will actually become:

	z = ((a++)*(a++));

Which will not produce correct results in certain situations.  If a=7
for example, then:

	a = 7;
	z = ((7)*(8));
	/* variable 'a' now has the value of 9 */

The bottom line is to be aware of side-effects when using macros.

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