Added comments explaining what the module provides. Removed BigUint for being overkill. Removed the use and returning of the variable m. Renamed the names of the test cases to something more logical.

Author: WinterPancake

src/math/triangular_number.rs

@@ -1,9 +1,12 @@
 // Triangular Numbers: Function to the Nth Triangular Number
 // Wikipedia Reference : https://en.wikipedia.org/wiki/Triangular_number
-use num_bigint::BigUint;
-pub fn triangular_number(n: u64) -> BigUint {
-    let m: BigUint = ((n | 1) * ((n + 1) / 2)).into();
-    m
+
+// This program provides a function to calculate the nth triangular number defined by T_n = 1 + 2 +
+// ... + n = (n^2 + 2)/ = n(n + 1)/2 = (n + 1) choose 2.
+
+//returns the nth triangular number
+pub fn triangular_number(n: u64) -> u64 {
+    (n | 1) * ((n + 1) / 2)
 }
 
 #[cfg(test)]
@@ -23,8 +26,11 @@ mod tests {
     }
 
     test_triangular_number! {
-        input_5: (6, BigUint::from(21u32)),
-        input_9: (10, BigUint::from(55u32)),
-        input_10: (100, BigUint::from(5050u32)),
+        input_0: (0, 0),
+        input_1: (1, 1),
+        input_2: (6, 21),
+        input_3: (10, 55),
+        input_4: (21, 231),
+        input_5: (100, 5050),
     }
 }