That said, it's entirely possible to program libraries in a way to
specifically allow full inlining of the libraries. The Data.Binary and
Data.Array.Vector libraries are written in this style for example,
which means lots of {-# INLINE #-} pragmas, maximum unfolding and high
optimisation levels.

-- Don

Every function has an inline pragma. Adding -O2 -funfolding-use-threshold999 -funfolding-creation-threshold999 does not significantly change the produced .hi files (--show-iface produces roughly the same files, just different headers) This makes sense to me because the library doesn't actually _do_ anything. There are no significant compiled functions, everything should be inlined. And since the .hi files are the same, I don't see why they wouldn't be. The two scenarios are these:

1) Library is installed via cabal.
2) Library source lives in the same directory as the application, so that ghc --make Examples.hs also builds the library.

When compiling the application I set all knobs to 11. In case 1, ./Examples 3000000 runs in 6.9s, case 2 in 5.2s. The module structure is the same in both cases, so I don't know what inlining across module boundaries has to do with it.

By the way, the library is now on hackage,
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Vec
but the documentation does not show up. What do I have to do to make this happen?

Scott