C style

[Guy Harris]

> > For Heaven's sake, the big problem with this code is that the conditional
> > is quite unreadable in in-line code like this.  I'd prefer
> >
> >	while (illegal (ch = getch()))
> >
> > (where "illegal" is defined as a function testing its character
> > argument). 
>
> It may enhance readability, but it's not worthwhile.  You've just managed
> to add a context switch per *character*.  Now, imagine what that's going to
> do to a program like spell.

Yes.  The System V "fgrep" uses a subroutine to do character comparisons.
The 4.2BSD version uses a macro instead.  The 4.2BSD version is
substantially faster.

The function "illegal" in the above example could have been defined as a
macro.  The code calling it would, of course, would have to be rewritten as

	for (;;) {
		ch = getch();
		if (ILLEGAL(ch))
			break;

or somesuch, since the macro uses its argument several times, and thus the
argument can't have side effects.  Mesa, C++, and other languages have the
notion of an "inline function"; when such a function is called, the compiler
doesn't generate a procedure call, but generates code that acts as if the
procedure in question had been called.  In the above example, the code as
written ("while (illegal(ch = getch))") would have compiled into code
equivalent to the macro version.

	Guy Harris