First of all rendering is not by definition I/O except in the trivial sense that all functions take input and produce output. A pure 3D rendering function takes game state as input and produces a list of triangles + attributes to draw as output.
Even if that were true it would only further validate my point.
> Do you have anything to back that up?
Yes, I already showed that Render.hs validates my point.
This is the claim we're talking about. Since you're into facts, not subjective opinions, show some evidence that the vast majority of the code in the repository is in the IO monad and uses carefully placed "!" eager evaluation annotations. Just to be clear, you haven't done that yet. That's a fact, not a subjective opinion.
https://github.com/rainbyte/frag/blob/master/src/BSP.hs
On every source file:
{-# LANGUAGE BangPatterns #-}https://github.com/rainbyte/frag/blob/master/src/BitSet.hs
https://github.com/rainbyte/frag/blob/master/src/Command.hs
https://github.com/rainbyte/frag/blob/master/src/Curves.hs
BangPatterns is a normal language extension to have enabled, was this used heavily? (hint: it's not enabled on "every source file.") You listed two of 28 files there, I'm assuming to try to show that the vast majority of the code in that repository is in the IO monad? You went from "vast majority" from one file to now two files. I'm looking for objectivity here, as you seem to be into. Let's see some numbers. I think anyone that glances at that repo would need some convincing of your claims.
Render.hs is 211 of 5580 lines of Haskell in the repository, by the way.