From 067f868222289d8e9433bc7b8a3f00705d22e100 Mon Sep 17 00:00:00 2001
From: Alex Mikhalev <alexmikhalevalex@gmail.com>
Date: Tue, 28 May 2019 10:59:19 -0700
Subject: [PATCH] Start working on solving systems of eqns

---
 src/math/eqn.rs | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/src/math/eqn.rs b/src/math/eqn.rs
index d54801d..fbbcb99 100644
--- a/src/math/eqn.rs
+++ b/src/math/eqn.rs
@@ -123,6 +123,22 @@ impl Unknowns for Eqns {
     }
 }
 
+impl fmt::Display for Eqns {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{{ ");
+        let mut first = true;
+        for eq in &self.0 {
+            if first {
+                first = false;
+            } else {
+                write!(f, " && ")?;
+            }
+            write!(f, "{}", eq)?
+        }
+        write!(f, " }}")
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -155,7 +171,7 @@ mod tests {
     }
 
     #[test]
-    fn test_solve() {
+    fn test_eqn_solve() {
         use Expr::*;
         let _ = env_logger::try_init();
         let u1 = Unknown(1);
@@ -232,4 +248,23 @@ mod tests {
         assert!(relative_eq!(const_expr(e.clone()).unwrap(), -9.));
     }
 
+    #[test]
+    fn test_eqns_solve() {
+       use Expr::*;
+
+        let x = Unknown(1);
+        let y = Unknown(2);
+        let t1 = Unknown(3);
+        let t2 = Unknown(4);
+
+        let eqns = Eqns(vec![
+            Eqn::new(x.into(), t1 / 2.),
+            Eqn::new(y.into(), t1 / 2.),
+            Eqn::new(x.into(), Const(1.0) - t2 / 2.),
+            Eqn::new(y.into(), t2 / 2.),
+        ]);
+        println!("eqns: {}", eqns);
+        let sol = eqns.solve(&[t1, t2]).unwrap();
+    }
+
 }