From 45cf1fcdf3d0663d70a21a39b1c60422bfedcb8a Mon Sep 17 00:00:00 2001
From: Ben Ruijl <benruyl@gmail.com>
Date: Sun, 28 Jul 2024 11:46:33 +0200
Subject: [PATCH] Add TryFrom<Atom> for i64 and Rational

- Add a method to get the coefficient ring from
  a polynomial ring
---
 src/coefficient.rs     | 64 ++++++++++++++++++++++++++++++++++++++++++
 src/poly/polynomial.rs |  5 ++++
 2 files changed, 69 insertions(+)

diff --git a/src/coefficient.rs b/src/coefficient.rs
index 2d21f8b4..35fc32b7 100644
--- a/src/coefficient.rs
+++ b/src/coefficient.rs
@@ -891,6 +891,70 @@ impl Add<i64> for CoefficientView<'_> {
     }
 }
 
+impl TryFrom<Atom> for i64 {
+    type Error = &'static str;
+
+    fn try_from(value: Atom) -> Result<Self, Self::Error> {
+        value.as_view().try_into()
+    }
+}
+
+impl TryFrom<&Atom> for i64 {
+    type Error = &'static str;
+
+    fn try_from(value: &Atom) -> Result<Self, Self::Error> {
+        value.as_view().try_into()
+    }
+}
+
+impl<'a> TryFrom<AtomView<'a>> for i64 {
+    type Error = &'static str;
+
+    fn try_from(value: AtomView<'a>) -> Result<Self, Self::Error> {
+        if let AtomView::Num(n) = value {
+            if let CoefficientView::Natural(n, 1) = n.get_coeff_view() {
+                return Ok(n);
+            } else {
+                Err("Not an i64")
+            }
+        } else {
+            Err("Not a number")
+        }
+    }
+}
+
+impl TryFrom<Atom> for Rational {
+    type Error = &'static str;
+
+    fn try_from(value: Atom) -> Result<Self, Self::Error> {
+        value.as_view().try_into()
+    }
+}
+
+impl TryFrom<&Atom> for Rational {
+    type Error = &'static str;
+
+    fn try_from(value: &Atom) -> Result<Self, Self::Error> {
+        value.as_view().try_into()
+    }
+}
+
+impl<'a> TryFrom<AtomView<'a>> for Rational {
+    type Error = &'static str;
+
+    fn try_from(value: AtomView<'a>) -> Result<Self, Self::Error> {
+        if let AtomView::Num(n) = value {
+            match n.get_coeff_view() {
+                CoefficientView::Natural(n, d) => Ok(Rational::from_unchecked(n, d)),
+                CoefficientView::Large(r) => Ok(r.to_rat()),
+                _ => Err("Not a rational"),
+            }
+        } else {
+            Err("Not a number")
+        }
+    }
+}
+
 impl Atom {
     /// Set the coefficient ring to the multivariate rational polynomial with `vars` variables.
     pub fn set_coefficient_ring(&self, vars: &Arc<Vec<Variable>>) -> Atom {
diff --git a/src/poly/polynomial.rs b/src/poly/polynomial.rs
index d2416bd5..c2e4bcd2 100755
--- a/src/poly/polynomial.rs
+++ b/src/poly/polynomial.rs
@@ -45,6 +45,11 @@ impl<R: Ring, E: Exponent> PolynomialRing<R, E> {
             _phantom_exp: PhantomData,
         }
     }
+
+    /// Get the coefficient ring.
+    pub fn coefficient_ring(&self) -> &R {
+        &self.ring
+    }
 }
 
 impl<R: Ring, E: Exponent> std::fmt::Display for PolynomialRing<R, E> {