[WalterBright]

D is compatible enough with C/C++ that I have been able to take largish multifile projects and convert them one file at a time to D. The full regression suite was run after each file was converted. This helped ensure both an accurate conversion and did not leave the project in a broken state for an extended period.

[WalterBright]

I've successfully converted many projects from one language to another using this method. One was a huge assembler program I converted to C back in the 1980s (ironically, so it could be ported to other platforms!).