diff --git a/src/math/solver.rs b/src/math/eqn.rs
similarity index 96%
rename from src/math/solver.rs
rename to src/math/eqn.rs
index f114a01..53ffb24 100644
--- a/src/math/solver.rs
+++ b/src/math/eqn.rs
@@ -6,11 +6,11 @@ use crate::math::Scalar;
 
 // an unknown variable with an id
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
-struct Unknown(i64);
+pub struct Unknown(i64);
 
-type UnknownSet = BTreeSet<Unknown>;
+pub type UnknownSet = BTreeSet<Unknown>;
 
-trait Unknowns {
+pub trait Unknowns {
     fn unknowns(&self) -> UnknownSet;
     fn has_unknowns(&self) -> bool;
     fn has_unknown(&self, u: Unknown) -> bool;
@@ -47,7 +47,7 @@ impl fmt::Display for Unknown {
 }
 
 #[derive(Clone, Debug, PartialEq)]
-enum Expr {
+pub enum Expr {
     Unkn(Unknown),
     Const(Scalar),
     Sum(Exprs),
@@ -56,7 +56,7 @@ enum Expr {
     Div(Box<Expr>, Box<Expr>),
 }
 
-type Exprs = Vec<Expr>;
+pub type Exprs = Vec<Expr>;
 
 impl Unknowns for Exprs {
     fn unknowns(&self) -> UnknownSet {
@@ -259,26 +259,26 @@ impl Unknowns for Expr {
 }
 
 impl Expr {
-    fn new_sum(e1: Expr, e2: Expr) -> Expr {
+    pub fn new_sum(e1: Expr, e2: Expr) -> Expr {
         Expr::Sum(vec![e1, e2])
     }
-    fn new_product(e1: Expr, e2: Expr) -> Expr {
+    pub fn new_product(e1: Expr, e2: Expr) -> Expr {
         Expr::Product(vec![e1, e2])
     }
-    fn new_neg(e1: Expr) -> Expr {
+    pub fn new_neg(e1: Expr) -> Expr {
         Expr::Neg(Box::new(e1))
     }
-    fn new_div(num: Expr, den: Expr) -> Expr {
+    pub fn new_div(num: Expr, den: Expr) -> Expr {
         Expr::Div(Box::new(num), Box::new(den))
     }
-    fn new_minus(e1: Expr, e2: Expr) -> Expr {
+    pub fn new_minus(e1: Expr, e2: Expr) -> Expr {
         Expr::Sum(vec![e1, Expr::new_neg(e2)])
     }
-    fn new_inv(den: Expr) -> Expr {
+    pub fn new_inv(den: Expr) -> Expr {
         Expr::new_div(Expr::Const(1.), den)
     }
 
-    fn is_zero(&self) -> bool {
+    pub fn is_zero(&self) -> bool {
         use Expr::*;
         match self {
             Const(c) => relative_eq!(*c, 0.),
@@ -286,7 +286,7 @@ impl Expr {
         }
     }
 
-    fn is_one(&self) -> bool {
+    pub fn is_one(&self) -> bool {
         use Expr::*;
         match self {
             Const(c) => relative_eq!(*c, 1.),
@@ -294,7 +294,7 @@ impl Expr {
         }
     }
 
-    fn simplify(self) -> Expr {
+    pub fn simplify(self) -> Expr {
         use Expr::*;
         match self {
             Sum(es) => {
@@ -384,7 +384,7 @@ impl Expr {
         }
     }
 
-    fn distribute(self) -> Expr {
+    pub fn distribute(self) -> Expr {
         use Expr::*;
         trace!("distribute {}", self);
         match self {
@@ -444,7 +444,7 @@ impl fmt::Display for Expr {
 }
 
 #[derive(Clone, Debug, PartialEq)]
-struct Eqn(Expr, Expr);
+pub struct Eqn(Expr, Expr);
 
 impl Unknowns for Eqn {
     fn unknowns(&self) -> UnknownSet {
@@ -473,11 +473,15 @@ fn ord_by_unkn(a: Expr, b: Expr, u: Unknown) -> Option<(Expr, Expr)> {
 }
 
 impl Eqn {
-    fn simplify(self) -> Eqn {
+    pub fn new(l: Expr, r: Expr) -> Self {
+        Self(l, r)
+    }
+
+    pub fn simplify(self) -> Eqn {
         Eqn(self.0.simplify(), self.1.simplify())
     }
 
-    fn solve(&self, for_u: Unknown) -> Option<Expr> {
+    pub fn solve(&self, for_u: Unknown) -> Option<Expr> {
         use Expr::*;
         if !self.has_unknown(for_u) {
             return None;
@@ -528,7 +532,6 @@ impl Eqn {
                     }
                 }
                 Const(_) => return None,
-                _ => return None,
             };
             l = new_l;
             r = new_r;
@@ -543,7 +546,7 @@ impl fmt::Display for Eqn {
 }
 
 #[derive(Clone, Debug, PartialEq)]
-struct Eqns(Vec<Eqn>);
+pub struct Eqns(Vec<Eqn>);
 
 impl Unknowns for Eqns {
     fn unknowns(&self) -> UnknownSet {
diff --git a/src/math/mod.rs b/src/math/mod.rs
index 88d0fb5..d6936be 100644
--- a/src/math/mod.rs
+++ b/src/math/mod.rs
@@ -1,4 +1,4 @@
-pub mod solver;
+pub mod eqn;
 
 pub type Scalar = f64;