C Primer Plus, Fourth Edition

Chapter 16

1:

Here are groups of one or more macros followed by a source code line that uses them. What code results in each case? Is it valid code? (Assume C variables have been declared.) #define FPM 5280 /* feet per mile */ dist = FPM * miles; #define FEET 4 #define POD FEET + FEET plort = FEET * POD; #define SIX = 6; nex = SIX; #define NEW(X) X + 5 y = NEW(y); berg = NEW(berg) * lob; est = NEW(berg) / NEW(y); nilp = lob * NEW(-berg);

A1:

dist = 5280 * miles; is valid. plort = 4 * 4 + 4; is valid. But if the user really wanted 4 * (4 + 4), he or she should have used #define POD (FEET + FEET). nex = = 6;; is valid, but not meaningful. Apparently, the user forgot that he or she was writing for the preprocessor, not writing in C. y = y + 5; ...