Cover fe ature 47 january 2012 Published by the ieee computer Society 0018-9162/12/$31. 00 2012 ieee

if 

(x.c) f1(x) else f2(x)

.

Using an if-statement is the least structured and most 

flexible option. However, we should choose the more struc-

tured and easier-to-optimize alternatives whenever possible. 

The hierarchy option can be most useful, but was seriously 

overused in the past couple of decades. Not every class natu-

rally belongs in a hierarchy, not every class benefits from the 

coupling that a hierarchy introduces, and not every class is 

improved by the possibility of adding to it through deriva-

tion (subclassing). Of the alternatives, a call of an ordinary 

function is the easiest to understand—it’s also often easy 

to inline. Consequently, overloading—statically selecting a 

function based on argument types—can lead to major ef-

ficiency advantages compared to indirect calls (as used to 

select among alternatives in a class hierarchy).

To become significantly more reliable, code must 

become more transparent. In particular, nested conditions