From 7ec4785a5ae6ce18bfb5b6eb993d7c222208108a Mon Sep 17 00:00:00 2001
From: Harsh Kumar <61012869+cyrixninja@users.noreply.github.com>
Date: Sun, 29 Oct 2023 01:58:55 +0530
Subject: [PATCH] Add Geometric Series (#595)

---
 src/math/geometric_series.rs | 56 ++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 src/math/geometric_series.rs

diff --git a/src/math/geometric_series.rs b/src/math/geometric_series.rs
new file mode 100644
index 00000000000..d2900768726
--- /dev/null
+++ b/src/math/geometric_series.rs
@@ -0,0 +1,56 @@
+// Author : cyrixninja
+// Wikipedia : https://en.wikipedia.org/wiki/Geometric_series
+// Calculate a geometric series.
+
+fn geometric_series(nth_term: f64, start_term_a: f64, common_ratio_r: f64) -> Vec<f64> {
+    let mut series = Vec::new();
+    let mut multiple = 1.0;
+
+    for _ in 0..(nth_term as i32) {
+        series.push(start_term_a * multiple);
+        multiple *= common_ratio_r;
+    }
+
+    series
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn assert_approx_eq(a: f64, b: f64) {
+        let epsilon = 1e-10;
+        assert!(
+            (a - b).abs() < epsilon,
+            "Expected {}, found {}",
+            a,
+            b
+        );
+    }
+
+    #[test]
+    fn test_geometric_series() {
+        let result = geometric_series(4.0, 2.0, 2.0);
+        assert_eq!(result.len(), 4);
+        assert_approx_eq(result[0], 2.0);
+        assert_approx_eq(result[1], 4.0);
+        assert_approx_eq(result[2], 8.0);
+        assert_approx_eq(result[3], 16.0);
+
+        let result = geometric_series(4.1, 2.1, 2.1);
+        assert_eq!(result.len(), 4);
+        assert_approx_eq(result[0], 2.1);
+        assert_approx_eq(result[1], 4.41);
+        assert_approx_eq(result[2], 9.261);
+        assert_approx_eq(result[3], 19.4481);
+
+        let result = geometric_series(4.0, -2.0, 2.0);
+        assert_eq!(result.len(), 4);
+        assert_approx_eq(result[0], -2.0);
+        assert_approx_eq(result[1], -4.0);
+        assert_approx_eq(result[2], -8.0);
+        assert_approx_eq(result[3], -16.0);
+
+    }
+}