From 5c64817f797c572394e7a32be79f91893d819a65 Mon Sep 17 00:00:00 2001
From: Michael Coady <mcoady@gmail.com>
Date: Wed, 21 Jan 2026 02:10:10 +0000
Subject: [PATCH 1/2] fix `writeCsv` for `OptionalColumn`  writing `Maybe a`
 values instead of `a` values

---
 src/DataFrame/IO/CSV.hs      | 6 +-----
 src/DataFrame/Lazy/IO/CSV.hs | 6 +-----
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/src/DataFrame/IO/CSV.hs b/src/DataFrame/IO/CSV.hs
index 1a055d2..5386fbb 100644
--- a/src/DataFrame/IO/CSV.hs
+++ b/src/DataFrame/IO/CSV.hs
@@ -428,11 +428,7 @@ getRowAsText df i = V.ifoldr go [] (columns df)
                     ++ "the other columns at index "
                     ++ show i
     go k (OptionalColumn (c :: V.Vector (Maybe a))) acc = case c V.!? i of
-        Just e -> textRep : acc
-          where
-            textRep = case testEquality (typeRep @a) (typeRep @T.Text) of
-                Just Refl -> fromMaybe "Nothing" e
-                Nothing -> (T.pack . show) e
+        Just e -> maybe T.empty T.show e : acc
         Nothing ->
             error $
                 "Column "
diff --git a/src/DataFrame/Lazy/IO/CSV.hs b/src/DataFrame/Lazy/IO/CSV.hs
index a1bc795..ecaacde 100644
--- a/src/DataFrame/Lazy/IO/CSV.hs
+++ b/src/DataFrame/Lazy/IO/CSV.hs
@@ -383,11 +383,7 @@ getRowAsText df i = V.ifoldr go [] (columns df)
                     ++ "the other columns at index "
                     ++ show i
     go k (OptionalColumn (c :: V.Vector (Maybe a))) acc = case c V.!? i of
-        Just e -> textRep : acc
-          where
-            textRep = case testEquality (typeRep @a) (typeRep @T.Text) of
-                Just Refl -> fromMaybe "Nothing" e
-                Nothing -> (T.pack . show) e
+        Just e -> maybe T.empty T.show e : acc
         Nothing ->
             error $
                 "Column "

From d0f6b5a3fdb7bd1f412aa3da7f987363ba63a421 Mon Sep 17 00:00:00 2001
From: Michael Coady <mcoady@gmail.com>
Date: Wed, 21 Jan 2026 10:50:20 +0000
Subject: [PATCH 2/2] replace use of `Text.show` and handle `OptionalColumn` of
 `Maybe Text` separately

---
 src/DataFrame/IO/CSV.hs      | 4 +++-
 src/DataFrame/Lazy/IO/CSV.hs | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/DataFrame/IO/CSV.hs b/src/DataFrame/IO/CSV.hs
index 5386fbb..450cb3c 100644
--- a/src/DataFrame/IO/CSV.hs
+++ b/src/DataFrame/IO/CSV.hs
@@ -428,7 +428,9 @@ getRowAsText df i = V.ifoldr go [] (columns df)
                     ++ "the other columns at index "
                     ++ show i
     go k (OptionalColumn (c :: V.Vector (Maybe a))) acc = case c V.!? i of
-        Just e -> maybe T.empty T.show e : acc
+        Just e -> case testEquality (typeRep @a) (typeRep @T.Text) of
+            Just Refl -> fromMaybe T.empty e : acc
+            Nothing -> maybe T.empty (T.pack . show) e : acc
         Nothing ->
             error $
                 "Column "
diff --git a/src/DataFrame/Lazy/IO/CSV.hs b/src/DataFrame/Lazy/IO/CSV.hs
index ecaacde..734e7e3 100644
--- a/src/DataFrame/Lazy/IO/CSV.hs
+++ b/src/DataFrame/Lazy/IO/CSV.hs
@@ -383,7 +383,9 @@ getRowAsText df i = V.ifoldr go [] (columns df)
                     ++ "the other columns at index "
                     ++ show i
     go k (OptionalColumn (c :: V.Vector (Maybe a))) acc = case c V.!? i of
-        Just e -> maybe T.empty T.show e : acc
+        Just e -> case testEquality (typeRep @a) (typeRep @T.Text) of
+            Just Refl -> fromMaybe T.empty e : acc
+            Nothing -> maybe T.empty (T.pack . show) e : acc
         Nothing ->
             error $
                 "Column "