From 20f7d7be13cd7869b338f98d1ab3fd33e8bbfb3e Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom@tomsmeding.com>
Date: Thu, 27 Nov 2025 21:30:17 +0100
Subject: WIP user-specified custom types

The big roadblock encountered is that accumulation wants addition of
monoids to be elementwise float addition; this fundamentally clashes
with the concept of a user type with a custom zero and plus.
---
 src/CHAD/ForwardAD.hs | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'src/CHAD/ForwardAD.hs')

diff --git a/src/CHAD/ForwardAD.hs b/src/CHAD/ForwardAD.hs
index 0ae88ce..933a259 100644
--- a/src/CHAD/ForwardAD.hs
+++ b/src/CHAD/ForwardAD.hs
@@ -57,6 +57,7 @@ tanty (STScal t) = case t of
   STF64 -> STScal STF64
   STBool -> STNil
 tanty STAccum{} = error "Accumulators not allowed in input program"
+tanty STUser{} = error "User types not yet supported in forward AD"
 
 tanenv :: SList STy env -> SList STy (TanE env)
 tanenv SNil = SNil
@@ -79,6 +80,7 @@ zeroTan (STScal STF32) _ = 0.0
 zeroTan (STScal STF64) _ = 0.0
 zeroTan (STScal STBool) _ = ()
 zeroTan STAccum{} _ = error "Accumulators not allowed in input program"
+zeroTan STUser{} _ = error "User types not yet supported in forward AD"
 
 tanScalars :: STy t -> Rep (Tan t) -> [Double]
 tanScalars STNil () = []
@@ -97,6 +99,7 @@ tanScalars (STScal STF32) x = [realToFrac x]
 tanScalars (STScal STF64) x = [x]
 tanScalars (STScal STBool) _ = []
 tanScalars STAccum{} _ = error "Accumulators not allowed in input program"
+tanScalars STUser{} _ = []
 
 tanEScalars :: SList STy env -> SList Value (TanE env) -> [Double]
 tanEScalars SNil SNil = []
@@ -128,6 +131,7 @@ unzipDN (STScal ty) d = case ty of
   STF64 -> d
   STBool -> (d, ())
 unzipDN STAccum{} _ = error "Accumulators not allowed in input program"
+unzipDN STUser{} _ = error "User types not yet supported in forward AD"
 
 dotprodTan :: STy t -> Rep (Tan t) -> Rep (Tan t) -> Double
 dotprodTan STNil _ _ = 0.0
@@ -160,6 +164,7 @@ dotprodTan (STScal ty) x y = case ty of
   STF64 -> x * y
   STBool -> 0.0
 dotprodTan STAccum{} _ _ = error "Accumulators not allowed in input program"
+dotprodTan STUser{} _ _ = 0.0
 
 -- -- Primal expression must be duplicable
 -- dnConstE :: STy t -> Ex env t -> Ex env (DN t)
@@ -198,6 +203,7 @@ dnConst (STScal t) = case t of
   STF64 -> (,0.0)
   STBool -> id
 dnConst STAccum{} = error "Accumulators not allowed in input program"
+dnConst STUser{} = error "User types not yet supported in forward AD"
 
 -- | Given a function that computes the forward derivative for a particular
 -- dual-numbers input, a 'RevByFwd' computes the gradient with respect to this
@@ -233,6 +239,7 @@ dnOnehots (STScal t) x = case t of
   STF64 -> \f -> f (x, 1.0)
   STBool -> \_ -> ()
 dnOnehots STAccum{} _ = error "Accumulators not allowed in input program"
+dnOnehots ty@STUser{} x = const (zeroTan ty x)
 
 dnConstEnv :: SList STy env -> SList Value env -> SList Value (DNE env)
 dnConstEnv SNil SNil = SNil
-- 
cgit v1.2.3-70-g09d2