Index: Cargo.toml
==================================================================
--- Cargo.toml
+++ Cargo.toml
@@ -1,8 +1,8 @@
 [package]
 name = "strval"
-version = "0.3.0"
+version = "0.3.1"
 edition = "2024"
 license = "0BSD"
 # https://crates.io/category_slugs
 categories = ["text-processing"]
 keywords = ["parsing", "string", "rusqlite"]

Index: src/binu64count.rs
==================================================================
--- src/binu64count.rs
+++ src/binu64count.rs
@@ -1,6 +1,6 @@
-use std::{marker::PhantomData, str::FromStr};
+use std::{fmt, marker::PhantomData, str::FromStr};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -66,10 +66,16 @@
 impl<C> AsRef<str> for BinU64Count<C> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<C> fmt::Display for BinU64Count<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<C> FromStr for BinU64Count<C> {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/binu64size.rs
==================================================================
--- src/binu64size.rs
+++ src/binu64size.rs
@@ -1,6 +1,6 @@
-use std::{marker::PhantomData, str::FromStr};
+use std::{fmt, marker::PhantomData, str::FromStr};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -66,10 +66,16 @@
 impl<C> AsRef<str> for BinU64Size<C> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<C> fmt::Display for BinU64Size<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<C> FromStr for BinU64Size<C> {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/binusizecount.rs
==================================================================
--- src/binusizecount.rs
+++ src/binusizecount.rs
@@ -1,6 +1,6 @@
-use std::{marker::PhantomData, str::FromStr};
+use std::{fmt, marker::PhantomData, str::FromStr};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -66,10 +66,16 @@
 impl<C> AsRef<str> for BinUsizeCount<C> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<C> fmt::Display for BinUsizeCount<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<C> FromStr for BinUsizeCount<C> {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/binusizesize.rs
==================================================================
--- src/binusizesize.rs
+++ src/binusizesize.rs
@@ -1,6 +1,6 @@
-use std::{marker::PhantomData, str::FromStr};
+use std::{fmt, marker::PhantomData, str::FromStr};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -66,10 +66,16 @@
 impl<C> AsRef<str> for BinUsizeSize<C> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<C> fmt::Display for BinUsizeSize<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<C> FromStr for BinUsizeSize<C> {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/boolean.rs
==================================================================
--- src/boolean.rs
+++ src/boolean.rs
@@ -1,6 +1,6 @@
-use std::str::FromStr;
+use std::{fmt, str::FromStr};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -58,10 +58,16 @@
 impl AsRef<str> for Bool {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl fmt::Display for Bool {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl FromStr for Bool {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/decu64count.rs
==================================================================
--- src/decu64count.rs
+++ src/decu64count.rs
@@ -1,6 +1,6 @@
-use std::{marker::PhantomData, str::FromStr};
+use std::{fmt, marker::PhantomData, str::FromStr};
 
 use parse_size::ByteSuffix;
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
@@ -66,10 +66,16 @@
 impl<C> AsRef<str> for DecU64Count<C> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<C> fmt::Display for DecU64Count<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<C> FromStr for DecU64Count<C> {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/decu64size.rs
==================================================================
--- src/decu64size.rs
+++ src/decu64size.rs
@@ -1,6 +1,6 @@
-use std::{marker::PhantomData, str::FromStr};
+use std::{fmt, marker::PhantomData, str::FromStr};
 
 use parse_size::ByteSuffix;
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
@@ -65,10 +65,16 @@
 impl<C> AsRef<str> for DecU64Size<C> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<C> fmt::Display for DecU64Size<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<C> FromStr for DecU64Size<C> {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/decusizecount.rs
==================================================================
--- src/decusizecount.rs
+++ src/decusizecount.rs
@@ -1,6 +1,6 @@
-use std::{marker::PhantomData, str::FromStr};
+use std::{fmt, marker::PhantomData, str::FromStr};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -66,10 +66,16 @@
 impl<C> AsRef<str> for DecUsizeCount<C> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<C> fmt::Display for DecUsizeCount<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<C> FromStr for DecUsizeCount<C> {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/decusizesize.rs
==================================================================
--- src/decusizesize.rs
+++ src/decusizesize.rs
@@ -1,6 +1,6 @@
-use std::{marker::PhantomData, str::FromStr};
+use std::{fmt, marker::PhantomData, str::FromStr};
 
 use parse_size::ByteSuffix;
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
@@ -65,10 +65,16 @@
 impl<C> AsRef<str> for DecUsizeSize<C> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<C> fmt::Display for DecUsizeSize<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<C> FromStr for DecUsizeSize<C> {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/dur.rs
==================================================================
--- src/dur.rs
+++ src/dur.rs
@@ -1,6 +1,6 @@
-use std::{marker::PhantomData, str::FromStr, time::Duration};
+use std::{fmt, marker::PhantomData, str::FromStr, time::Duration};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -71,10 +71,16 @@
 impl<C> AsRef<str> for Dur<C> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<C> fmt::Display for Dur<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<C> FromStr for Dur<C> {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/percent.rs
==================================================================
--- src/percent.rs
+++ src/percent.rs
@@ -1,8 +1,8 @@
 //! Relative or absolute limit.
 
-use std::str::FromStr;
+use std::{fmt, str::FromStr};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -54,10 +54,16 @@
 impl AsRef<str> for Percent {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl fmt::Display for Percent {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl FromStr for Percent {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/relabslim.rs
==================================================================
--- src/relabslim.rs
+++ src/relabslim.rs
@@ -1,8 +1,8 @@
 //! Relative or absolute limit.
 
-use std::{marker::PhantomData, str::FromStr};
+use std::{fmt, marker::PhantomData, str::FromStr};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -102,10 +102,16 @@
 impl<C> AsRef<str> for RelAbsLim<C> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<C> fmt::Display for RelAbsLim<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<C> FromStr for RelAbsLim<C> {
   type Err = Error;
 
   fn from_str(s: &str) -> Result<Self, Self::Err> {

Index: src/select.rs
==================================================================
--- src/select.rs
+++ src/select.rs
@@ -1,6 +1,6 @@
-use std::str::FromStr;
+use std::{fmt, str::FromStr};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -56,10 +56,16 @@
 impl<E> AsRef<str> for Select<E> {
   fn as_ref(&self) -> &str {
     &self.sval
   }
 }
+
+impl<E> fmt::Display for Select<E> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.sval)
+  }
+}
 
 impl<E> FromStr for Select<E>
 where
   E: FromStr
 {

Index: src/str.rs
==================================================================
--- src/str.rs
+++ src/str.rs
@@ -1,6 +1,6 @@
-use std::{marker::PhantomData, str::FromStr};
+use std::{fmt, marker::PhantomData, str::FromStr};
 
 #[cfg(feature = "rusqlite")]
 use rusqlite::{
   ToSql,
   types::{FromSql, FromSqlError, FromSqlResult, ToSqlOutput, ValueRef}
@@ -63,10 +63,16 @@
 impl<C> AsRef<str> for Str<C> {
   fn as_ref(&self) -> &str {
     &self.val
   }
 }
+
+impl<C> fmt::Display for Str<C> {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    write!(f, "{}", self.val)
+  }
+}
 
 impl<C> FromStr for Str<C>
 where
   C: Controller<Type = String>
 {

Index: www/changelog.md
==================================================================
--- www/changelog.md
+++ www/changelog.md
@@ -2,18 +2,28 @@
 
 ⚠️  indicates a breaking change.
 
 ## [Unreleased]
 
-[Details](/vdiff?from=strval-0.3.0&to=trunk)
+[Details](/vdiff?from=strval-0.3.1&to=trunk)
 
 ### Added
 
 ### Changed
 
 ### Removed
 
+---
+
+## [0.3.1] - 2025-07-30
+
+[Details](/vdiff?from=strval-0.3.0&to=strval-0.3.1)
+
+### Added
+
+- Implement `Display` for data types.  Returns the string representation.
+
 ---
 
 ## [0.3.0] - 2025-07-29
 
 [Details](/vdiff?from=strval-0.2.0&to=strval-0.3.0)