From 04a3d5200729a512856d3060dd6609b208a37b4d Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@github.com>
Date: Thu, 4 Aug 2016 12:13:48 -0400
Subject: [PATCH] :memo: diffTerms.

---
 src/Interpreter.hs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/Interpreter.hs b/src/Interpreter.hs
index d4264797c..d8f1ddd18 100644
--- a/src/Interpreter.hs
+++ b/src/Interpreter.hs
@@ -24,8 +24,14 @@ type Comparable leaf annotation = Term leaf annotation -> Term leaf annotation -
 -- | Constructs a diff from the CofreeF containing its annotation and syntax. This function has the opportunity to, for example, cache properties in the annotation.
 type DiffConstructor leaf annotation = CofreeF (Syntax leaf) (Both annotation) (Diff leaf annotation) -> Diff leaf annotation
 
--- | Diff two terms, given a function that determines whether two terms can be compared and a cost function.
-diffTerms :: (Eq leaf, Hashable leaf, Eq (Record fields), HasField fields Category) => DiffConstructor leaf (Record fields) -> Comparable leaf (Record fields) -> SES.Cost (Diff leaf (Record fields)) -> Term leaf (Record fields) -> Term leaf (Record fields) -> Diff leaf (Record fields)
+-- | Diff two terms recursively, given functions characterizing the diffing.
+diffTerms :: (Eq leaf, Hashable leaf, Eq (Record fields), HasField fields Category) =>
+  DiffConstructor leaf (Record fields) -> -- ^ A function to wrap up & possibly annotate every produced diff.
+  Comparable leaf (Record fields) -> -- ^ A function to determine whether or not two terms should even be compared.
+  SES.Cost (Diff leaf (Record fields)) -> -- ^ A function to compute the cost of a given diff node.
+  Term leaf (Record fields) -> -- ^ A term representing the old state.
+  Term leaf (Record fields) -> -- ^ A term representing the new state.
+  Diff leaf (Record fields)
 diffTerms construct comparable cost a b = fromMaybe (replacing a b) $ diffComparableTerms construct comparable cost a b
 
 diffComparableTerms :: (Eq leaf, Hashable leaf, Eq (Record fields), HasField fields Category) => DiffConstructor leaf (Record fields) -> Comparable leaf (Record fields) -> SES.Cost (Diff leaf (Record fields)) -> Term leaf (Record fields) -> Term leaf (Record fields) -> Maybe (Diff leaf (Record fields))