Added better explanation to functionality of rising_factorial.rs as well as comments for the all of the test cases. Also added comments to test cases for simplicial_polytopic_number.rs.

Author: WinterPancake

src/math/rising_factorial.rs

@@ -7,7 +7,8 @@ use std::ops::Mul;
 // https://mathworld.wolfram.com/RisingFactorial.html
 // https://en.wikipedia.org/wiki/Falling_and_rising_factorials
 //
-// Returns the nth rising factorial.
+// Returns the nth rising factorial. Which is calculated by giving the nth term and then
+// substituting our desired x; i.e. rising_factorial(4, 5) would give 4 * 5 * 6 * 7 * 8 = 6720.
 pub fn rising_factorial(x: u64, n: u64) -> u64 {
     let mut result = x;
     for i in 1..n {
@@ -23,11 +24,11 @@ mod tests {
 
     #[test]
     fn test_rising_factorial() {
-        assert_eq!(rising_factorial(1, 0), 1);
-        assert_eq!(rising_factorial(1, 1), 1);
-        assert_eq!(rising_factorial(2, 1), 2);
-        assert_eq!(rising_factorial(1, 2), 2); // 1 * 2
-        assert_eq!(rising_factorial(2, 2), 6); // 2 * 3
-        assert_eq!(rising_factorial(3, 3), 60); // 3 * 4 * 5
+        assert_eq!(rising_factorial(1, 0), 1); // 0! = 1
+        assert_eq!(rising_factorial(1, 1), 1); // 1 = 1
+        assert_eq!(rising_factorial(2, 1), 2); // 2 = 2
+        assert_eq!(rising_factorial(1, 2), 2); // 1 * 2 = 2
+        assert_eq!(rising_factorial(2, 2), 6); // 2 * 3 = 6
+        assert_eq!(rising_factorial(3, 3), 60); // 3 * 4 * 5 = 60
     }
 }

src/math/simplicial_polytopic_number.rs

@@ -36,13 +36,13 @@ mod tests {
     }
 
     test_simplicial_polytopic_number! {
-        input_0: ((1, 1), 1),
-        input_1: ((2, 1), 2),
-        input_2: ((2, 2), 3),
-        input_3: ((3, 3), 10),
-        input_4: ((2, 4), 5),
-        input_5: ((5, 5), 126),
-        input_6: ((9, 6), 3003),
-        input_7: ((6, 10), 3003),
+        input_0: ((1, 1), 1), // 1st natural number = 1
+        input_1: ((2, 1), 2), // 2nd natural number = 2
+        input_2: ((2, 2), 3), // 2nd triangular number = 3
+        input_3: ((3, 3), 10), // 3rd tetrahedral number = 10
+        input_4: ((2, 4), 5), // 2nd pentatope number = 5
+        input_5: ((5, 5), 126), // 5th 5_simplex = 126
+        input_6: ((9, 6), 3003), // 9th 6_simplex = 3003
+        input_7: ((6, 10), 3003), // 6th 10_simplex = 3003
     }
 }