[Haskell-cafe] Re. Looking for exemplars of "boring" or "simple" Haskell projects...

Rishiyur Nikhil nikhil at acm.org
Wed Jul 28 15:00:32 UTC 2021

A couple of years ago I wrote "Forvis", a "complete" semantics of the
RISC-V instruction set in "extremely elementary" Haskell.

It's free and open-source, at:

"Extremely Elementary" Haskell: small subset of Haskell 98.  No
    type classes, no monads (except the top-level driver that uses
    standard IO), no GHC extensions, nothing.  Just vanilla function
    definitions and vanilla algebraic types (a "Miranda" subset).

    Motivation: appeal to hardware designers, compiler writers, and others
    who are keenly interested in a clearly readable and executable precise
    spec of RISC-V semantics, but are not at all interested in learning

It's about 12K-13K lines of Haskell, all in one 'src/' directory.

Full "standard ISA" coverage:

- Unprivileged ISA:
    - RV32I (32-bit) and RV64I (64-bit) basic Integer instructions
    - Standard ISA extensions M (Integer Mult/Div), A (Atomics), C
        (Compressed) and FD (Single- and Double-precision floating

- Privileged ISA: Modes M (Machine), S (Supervisor) and U (User),
     including full complement of CSRs (Control and Status Registers).
     This includes full trap and interrupt handling, and RISC-V
     Virtual Memory schemes Sv32, Sv39 and Sv48.

I've tested it on all the standard RISC-V ISA tests (pass), booted a
Linux kernel (about 200 Million RISC-V Instructions), and the much
smaller real-time OS FreeRTOS.  I'm sure it'll work for any other
RISC-V software as well.  For this, the sources contain additional
code to package the "CPU" into a small "system", by adding Haskell
models of memory and a UART.

I haven't looked at it since early 2020, but it should all still work fine.

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