From 101a37b6bcabae56e79f3c103723f90cec9da094 Mon Sep 17 00:00:00 2001
From: Timothy Warren <twarren@nabancard.com>
Date: Thu, 5 Mar 2020 16:24:33 -0500
Subject: [PATCH] Tests and fixes

---
 Dockerfile    |  3 ---
 Jenkinsfile   |  1 +
 src/bigint.rs | 25 +++++++++++++++++--------
 src/lib.rs    | 30 ++++++++++++++++++++++++++----
 4 files changed, 44 insertions(+), 15 deletions(-)
 delete mode 100644 Dockerfile

diff --git a/Dockerfile b/Dockerfile
deleted file mode 100644
index 46f9341..0000000
--- a/Dockerfile
+++ /dev/null
@@ -1,3 +0,0 @@
-FROM rust:latest
-
-RUN cargo install cargo-tarpaulin
\ No newline at end of file
diff --git a/Jenkinsfile b/Jenkinsfile
index d394fdd..28d0739 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -18,6 +18,7 @@ pipeline {
      }
      stage('Coverage') {
          steps {
+             sh "cargo clean"
              sh "cargo install cargo-tarpaulin"
              sh "make generate-coverage"
          }
diff --git a/src/bigint.rs b/src/bigint.rs
index cbf9839..6ac5767 100644
--- a/src/bigint.rs
+++ b/src/bigint.rs
@@ -95,6 +95,7 @@ impl Add for BigInt {
     type Output = Self;
 
     fn add(self, rhs: Self) -> Self::Output {
+        // @TODO: handle signs
         let mut out = BigInt::default();
 
         let u_digits = self.inner.len();
@@ -112,14 +113,13 @@ impl Add for BigInt {
             let b = *rhs.inner.get(i).unwrap_or(&0usize);
 
             let (res, overflowed) = a.overflowing_add(b);
-            // assert!(!overflowed, "Expected to overflow: {:#?}", (res, overflowed));
             if overflowed {
                 if i == 0 {
-                    out.inner[i] = res;
+                    out.inner[i] = res + carry;
                 } else {
-                    out.inner.push(res);
+                    out.inner.push(res + carry);
                 }
-                carry = core::usize::MAX - res;
+                carry = 1;
             } else {
                 if res < core::usize::MAX {
                     out.inner.push(res + carry);
@@ -216,8 +216,9 @@ impl Not for BigInt {
     fn not(self) -> Self::Output {
         let mut flipped: Vec<usize> = Vec::with_capacity(self.inner.len());
 
-        for (i, val) in self.inner.iter().enumerate() {
-            flipped[i] = val.reverse_bits();
+        for val in self.inner.iter() {
+            let rev = !*val;
+            flipped.push(rev);
         }
 
         BigInt {
@@ -255,11 +256,19 @@ mod tests {
         );
         assert_eq!(sum.inner[1], 1usize, "most significant place should be 1");
 
-        /* let a = BigInt::from(core::usize::MAX);
+        let a = BigInt::from(core::usize::MAX);
         let b = BigInt::from(1usize);
         let sum = a + b;
         assert_eq!(sum.inner[0], 0usize);
-        assert_eq!(sum.inner[1], 1usize); */
+        assert_eq!(sum.inner[1], 1usize);
+    }
+
+    #[test]
+    fn test_not() {
+        let a = BigInt::from(0u8);
+        let b = !a;
+
+        assert_eq!(b.inner[0], core::usize::MAX);
     }
 
     #[test]
diff --git a/src/lib.rs b/src/lib.rs
index d2f0dc8..9ec36ad 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,8 +3,7 @@
 //! Playin' with Numerics in Rust
 #![forbid(unsafe_code)]
 
-use std::f64::consts::PI;
-use std::f64::consts::E;
+use std::f64::consts::{E, PI};
 
 pub mod bigint;
 pub mod num;
@@ -175,11 +174,34 @@ pub fn factorial(n: usize) -> Option<u128> {
     }
 }
 
-pub fn approx_factorial(n: f64) -> f64 {
+/// Approximates a factorial using Stirling's approximation
+///
+/// Based on https://en.wikipedia.org/wiki/Stirling's_approximation
+///
+/// Can approximate up to ~ 170.624!
+///
+/// Example:
+/// ```rust
+/// use rusty_numbers::approx_factorial;
+///
+/// let valid = approx_factorial(170.6); // Some(..)
+/// # assert!(valid.is_some());
+///
+/// let invalid = approx_factorial(171.0); // None
+/// # assert!(invalid.is_none());
+/// ```
+#[inline]
+pub fn approx_factorial(n: f64) -> Option<f64> {
     let power = (n / E).powf(n);
     let root = (PI * 2.0 * n).sqrt();
 
-    power * root
+    let res = power * root;
+
+    if res >= core::f64::MIN && res <= core::f64::MAX {
+        Some(res)
+    } else {
+        None
+    }
 }
 
 #[cfg(test)]