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

COVER FE ATURE

compUteR

 

50

We can improve code quality without 

adding runtime costs. 

developers simply precomputed answers and added them 

to the source code or as data inputs, which is rather ad 

hoc. In C, compile-time computation implies a rat’s nest 

of complicated and error-prone macros. Such computation 

is essentially untyped because most information must be 

encoded as integers. For infrastructure code, I suggest a 

more systematic and structured approach: type-rich pro-

gramming at compile time.

7

 The SI units example is an 

illustration.

Compile-time evaluation (and immutability in general) 

becomes more important as more systems become con-

current: You can’t have a data race on a constant.