Bitcoin F# is a full-node implementation in F# by hhanh00. Commenting on motivations on Bitcointalk, he says: <blockquote>I'm implementing a full node for a couple of things. 1. to make sure i have a complete understanding of the implementation that goes beyond reviewing code. For me, it's like reading a book versus writing one. 2. all the implementations i have seen follow a similar logic specially wrt blockchain management and scripting. i wanted to do it my way to see if it's better or worse. 3. i'm aiming for short. no wallet, no mining, no dos protection. These goals in mind, it is clearly not fit for wide distribution. It's working fine though - being able to sync up from the beginning while validating, holding a mempool content identical to the core client and etc.</blockquote>
Its project page on GitHub says: <blockquote>
- Bitcoin F# has fully validated the existing mainnet blockchain and passes all the integration tests including large reorg tests.
- It is also the only implementation in a functional language and comes under 2.5 kLOC, making it the smallest client too.
Commenting on its completeness on Bitcointalk, he says: <blockquote>it bootstraps, syncs and validates the blockchain. It passes the acceptance tests from Matt too. As a relay node, it keeps a tx pool, validates, relays new tx and you can trim old blocks just by deleting files. I've been running for a while. At about 2k lines of code, it fits my requirement of small code that I can fit in my brain but I understand it's not 100% compatible and will never be.</blockquote> There's a walkthrough of the (short!) code available.