From ddb4fe4f909434d59621b424e8138cb9c347e2d2 Mon Sep 17 00:00:00 2001
From: fkm3 <frederickmayle@gmail.com>
Date: Mon, 15 May 2017 22:09:21 -0700
Subject: [PATCH] Add ToTensor class

---
 tensorflow-ops/src/TensorFlow/Variable.hs |  5 ++++-
 tensorflow/src/TensorFlow/Tensor.hs       | 11 ++++++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/tensorflow-ops/src/TensorFlow/Variable.hs b/tensorflow-ops/src/TensorFlow/Variable.hs
index 548425d..141622f 100644
--- a/tensorflow-ops/src/TensorFlow/Variable.hs
+++ b/tensorflow-ops/src/TensorFlow/Variable.hs
@@ -30,7 +30,7 @@ import TensorFlow.Core
 import TensorFlow.Build (opDef)
 import TensorFlow.BuildOp (buildInputs, pureOp, OpParams)
 import TensorFlow.Output (opInputs, unNodeName)
-import TensorFlow.Tensor (Rendered(..), tensorNodeName)
+import TensorFlow.Tensor (Rendered(..), ToTensor(..), tensorNodeName)
 import TensorFlow.Types (tensorType)
 import qualified TensorFlow.GenOps.Core as CoreOps
 import TensorFlow.Ops (zeros)
@@ -40,6 +40,9 @@ newtype Variable a = Variable (Tensor Value ResourceHandle)
 instance Rendered Variable where
     renderedOutput (Variable v) = renderedOutput v
 
+instance ToTensor Variable where
+    toTensor = readValue
+
 -- | Creates a new, uninitialized variable.
 variable :: (MonadBuild m, TensorType a) => Shape -> m (Variable a)
 variable = variable' id
diff --git a/tensorflow/src/TensorFlow/Tensor.hs b/tensorflow/src/TensorFlow/Tensor.hs
index bce7a75..6ba1588 100644
--- a/tensorflow/src/TensorFlow/Tensor.hs
+++ b/tensorflow/src/TensorFlow/Tensor.hs
@@ -38,7 +38,8 @@ import Proto.Tensorflow.Core.Framework.NodeDef (device)
 import TensorFlow.Build
 import TensorFlow.Output (Output, NodeName, outputNodeName, Device(..))
 import TensorFlow.Types
-    ( TensorData(..)
+    ( TensorType
+    , TensorData(..)
     , ListOf(..)
     )
 import qualified TensorFlow.Internal.FFI as FFI
@@ -189,3 +190,11 @@ instance TensorKind Ref where
 
 instance TensorKind Build where
     toBuild = id
+
+
+-- | Types which can be converted to `Tensor`.
+class ToTensor t where
+    toTensor :: TensorType a => t a -> Tensor Build a
+
+instance TensorKind v => ToTensor (Tensor v) where
+    toTensor = expr