Is D actually |-----------this-----powerful-----------|?

[David Piepgrass]

Oops, forgot the code.

> "4. Unit inference engine: Given some notation for optionally 
> indicating units, e.g. unit(value), could a D metaprogram 
> examine the following code, infer the correct units, and issue 
> an error message on the last line?

auto mass = kg(2.0);
auto accel = 1.0;
auto force = mass*accel;
accel += metresPerSecondSquared(9.81); // units of 'force' and 
'accel' now known
force += pounds(3.0);                  // unit mismatch detected

P.S. And can D output 'pre-processed' source, i.e. the code after 
metaprograms have executed?