diff --git a/Cargo.lock b/Cargo.lock
index 13f27f1..7958e4e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -49,15 +49,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "approx"
-version = "0.3.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f0e60b75072ecd4168020818c0107f2857bb6c4e64252d8d3983f6263b40a5c3"
-dependencies = [
- "num-traits",
-]
-
 [[package]]
 name = "approx"
 version = "0.5.1"
@@ -371,7 +362,7 @@ dependencies = [
 name = "coremem_types"
 version = "0.1.0"
 dependencies = [
- "decorum",
+ "serde",
 ]
 
 [[package]]
@@ -556,18 +547,6 @@ dependencies = [
  "parking_lot_core 0.9.3",
 ]
 
-[[package]]
-name = "decorum"
-version = "0.3.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "281759d3c8a14f5c3f0c49363be56810fcd7f910422f97f2db850c2920fde5cf"
-dependencies = [
- "approx 0.3.2",
- "num-traits",
- "serde",
- "serde_derive",
-]
-
 [[package]]
 name = "deflate"
 version = "1.0.0"
@@ -1005,7 +984,7 @@ version = "0.23.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b6aee993351d466301a29655d628bfc6f5a35a0d062b6160ca0808f425805fd7"
 dependencies = [
- "approx 0.5.1",
+ "approx",
  "conv",
  "image",
  "itertools",
@@ -1289,7 +1268,7 @@ version = "0.30.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4fb2d0de08694bed883320212c18ee3008576bfe8c306f4c3c4a58b4876998be"
 dependencies = [
- "approx 0.5.1",
+ "approx",
  "matrixmultiply",
  "num-complex",
  "num-rational",
@@ -2006,7 +1985,7 @@ version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "13a2609e876d4f77f6ab7ff5254fc39b4f1927ba8e6db3d18be7c32534d3725e"
 dependencies = [
- "approx 0.5.1",
+ "approx",
  "num-complex",
  "num-traits",
  "paste",
diff --git a/crates/types/Cargo.toml b/crates/types/Cargo.toml
index 1621dc2..f016f66 100644
--- a/crates/types/Cargo.toml
+++ b/crates/types/Cargo.toml
@@ -5,4 +5,4 @@ authors = ["Colin <colin@uninsane.org>"]
 edition = "2021"
 
 [dependencies]
-decorum = "0.3"  # MIT
+serde = "1.0"  # MIT or Apache 2.0
diff --git a/crates/types/src/real.rs b/crates/types/src/real.rs
index b6db969..859752f 100644
--- a/crates/types/src/real.rs
+++ b/crates/types/src/real.rs
@@ -1,14 +1,12 @@
-use std::fmt;
+use core::fmt;
 use core::ops::{
     Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Sub, SubAssign,
 };
 use core::cmp::{Ordering, PartialOrd};
-
-// finite. non-nan, non-inf
-pub type R32 = decorum::R32;
-pub type R64 = decorum::R64;
+use serde::{Deserialize, Serialize};
 
 pub trait ToFloat {
+    // TODO: make these by-value
     fn to_f32(&self) -> f32 {
         self.to_f64() as _
     }
@@ -58,10 +56,12 @@ pub trait Real:
         Self::from_primitive(u)
     }
 
+    // TODO: make this by-value
     fn cast<R: Real>(&self) -> R {
         R::from_primitive(*self)
     }
 
+    fn is_finite(self) -> bool;
     fn floor(self) -> Self;
     fn ceil(self) -> Self;
     fn round(self) -> Self;
@@ -154,6 +154,9 @@ impl Real for f32 {
     fn from_f32(f: f32) -> Self {
         f
     }
+    fn is_finite(self) -> bool {
+        f32::is_finite(self)
+    }
     fn floor(self) -> Self {
         f32::floor(self)
     }
@@ -190,6 +193,9 @@ impl Real for f64 {
     fn from_f64(f: f64) -> Self {
         f
     }
+    fn is_finite(self) -> bool {
+        f64::is_finite(self)
+    }
     fn floor(self) -> Self {
         f64::floor(self)
     }
@@ -216,80 +222,125 @@ impl Real for f64 {
     }
 }
 
-impl ToFloat for R32 {
+#[derive(Default, Copy, Clone, Debug, PartialEq, PartialOrd, Serialize, Deserialize)]
+pub struct Finite<T>(T);
+
+pub type R32 = Finite<f32>;
+pub type R64 = Finite<f64>;
+
+impl<T: Real> Finite<T> {
+    fn new(inner: T) -> Self {
+        assert!(inner.is_finite(), "{:} is not finite", inner);
+        Self(inner)
+    }
+}
+
+impl<T: fmt::Display> fmt::Display for Finite<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl<T: fmt::LowerExp> fmt::LowerExp for Finite<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl<T: Real> Neg for Finite<T> {
+    type Output = Self;
+    fn neg(self) -> Self {
+        Self::new(self.0.neg())
+    }
+}
+
+impl<T: Real> AddAssign for Finite<T> {
+    fn add_assign(&mut self, other: Self) {
+        *self = Self::new(self.0.add(other.0))
+    }
+}
+impl<T: Real> SubAssign for Finite<T> {
+    fn sub_assign(&mut self, other: Self) {
+        *self = Self::new(self.0.sub(other.0))
+    }
+}
+impl<T: Real> MulAssign for Finite<T> {
+    fn mul_assign(&mut self, other: Self) {
+        *self = Self::new(self.0.mul(other.0))
+    }
+}
+impl<T: Real> DivAssign for Finite<T> {
+    fn div_assign(&mut self, other: Self) {
+        *self = Self::new(self.0.div(other.0))
+    }
+}
+
+impl<T: Real> Add for Finite<T> {
+    type Output = Self;
+    fn add(self, other: Self) -> Self {
+        Self::new(self.0.add(other.0))
+    }
+}
+impl<T: Real> Sub for Finite<T> {
+    type Output = Self;
+    fn sub(self, other: Self) -> Self {
+        Self::new(self.0.sub(other.0))
+    }
+}
+impl<T: Real> Mul for Finite<T> {
+    type Output = Self;
+    fn mul(self, other: Self) -> Self {
+        Self::new(self.0.mul(other.0))
+    }
+}
+impl<T: Real> Div for Finite<T> {
+    type Output = Self;
+    fn div(self, other: Self) -> Self {
+        Self::new(self.0.div(other.0))
+    }
+}
+
+
+impl<T: ToFloat> ToFloat for Finite<T> {
     fn to_f32(&self) -> f32 {
-        self.into_inner()
+        self.0.to_f32()
     }
-}
-
-impl Real for R32 {
-    fn from_primitive<P: ToFloat>(p: P) -> Self {
-        Self::from_f32(p.to_f32())
-    }
-    fn from_f32(f: f32) -> Self {
-        Self::from_inner(f)
-    }
-    fn floor(self) -> Self {
-        Self::from_primitive(self.into_inner().floor())
-    }
-    fn ceil(self) -> Self {
-        Self::from_primitive(self.into_inner().ceil())
-    }
-    fn round(self) -> Self {
-        Self::from_primitive(self.into_inner().round())
-    }
-    fn exp(self) -> Self {
-        Self::from_primitive(self.into_inner().exp())
-    }
-    fn powf(self, p: Self) -> Self {
-        Self::from_primitive(self.into_inner().powf(p.into_inner()))
-    }
-    fn sqrt(self) -> Self {
-        Self::from_primitive(self.into_inner().sqrt())
-    }
-    fn sin_cos(self) -> (Self, Self) {
-        let (s, c) = self.into_inner().sin_cos();
-        (Self::from_primitive(s), Self::from_primitive(c))
-    }
-    fn atan2(self, p: Self) -> Self {
-        Self::from_primitive(self.into_inner().atan2(p.into_inner()))
-    }
-}
-
-impl ToFloat for R64 {
     fn to_f64(&self) -> f64 {
-        self.into_inner()
+        self.0.to_f64()
     }
 }
 
-impl Real for R64 {
-    fn from_f64(f: f64) -> Self {
-        Self::from_inner(f)
+impl<T: Real> Real for Finite<T> {
+    fn from_primitive<P: ToFloat>(p: P) -> Self {
+        Self::new(T::from_primitive(p))
+    }
+    fn is_finite(self) -> bool {
+        true
     }
     fn floor(self) -> Self {
-        Self::from_primitive(self.into_inner().floor())
+        Self::new(self.0.floor())
     }
     fn ceil(self) -> Self {
-        Self::from_primitive(self.into_inner().ceil())
+        Self::new(self.0.ceil())
     }
     fn round(self) -> Self {
-        Self::from_primitive(self.into_inner().round())
+        Self::new(self.0.round())
     }
     fn exp(self) -> Self {
-        Self::from_primitive(self.into_inner().exp())
-    }
-    fn powf(self, p: Self) -> Self {
-        Self::from_primitive(self.into_inner().powf(p.into_inner()))
+        Self::new(self.0.exp())
     }
     fn sqrt(self) -> Self {
-        Self::from_primitive(self.into_inner().sqrt())
+        Self::new(self.0.sqrt())
     }
-    fn sin_cos(self) -> (Self, Self) {
-        let (s, c) = self.into_inner().sin_cos();
-        (Self::from_primitive(s), Self::from_primitive(c))
+    fn powf(self, p: Self) -> Self {
+        Self::new(self.0.powf(p.0))
     }
     fn atan2(self, p: Self) -> Self {
-        Self::from_primitive(self.into_inner().atan2(p.into_inner()))
+        Self::new(self.0.atan2(p.0))
+    }
+    fn sin_cos(self) -> (Self, Self) {
+        let (s, c) = self.0.sin_cos();
+        (Self::new(s), Self::new(c))
     }
 }