From 65aa43f0c8173b15b66c7fd79efb33992dc8b9e5 Mon Sep 17 00:00:00 2001
From: Defective Detective <71999854+SpiderMath@users.noreply.github.com>
Date: Wed, 16 Nov 2022 01:12:20 +0530
Subject: [PATCH] feat: Add signum (#419)

---
 src/math/mod.rs    |  2 ++
 src/math/signum.rs | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)
 create mode 100644 src/math/signum.rs

diff --git a/src/math/mod.rs b/src/math/mod.rs
index ff5aa79d8cc..ad4a19dd96a 100644
--- a/src/math/mod.rs
+++ b/src/math/mod.rs
@@ -31,6 +31,7 @@ mod prime_numbers;
 mod quadratic_residue;
 mod random;
 mod sieve_of_eratosthenes;
+mod signum;
 mod simpson_integration;
 mod square_root;
 mod trial_division;
@@ -76,6 +77,7 @@ pub use self::prime_numbers::prime_numbers;
 pub use self::quadratic_residue::cipolla;
 pub use self::random::PCG32;
 pub use self::sieve_of_eratosthenes::sieve_of_eratosthenes;
+pub use self::signum::signum;
 pub use self::simpson_integration::simpson_integration;
 pub use self::square_root::{fast_inv_sqrt, square_root};
 pub use self::trial_division::trial_division;
diff --git a/src/math/signum.rs b/src/math/signum.rs
new file mode 100644
index 00000000000..83b7e7b5538
--- /dev/null
+++ b/src/math/signum.rs
@@ -0,0 +1,36 @@
+/// Signum function is a mathematical function that extracts
+/// the sign of a real number. It is also known as the sign function,
+/// and it is an odd piecewise function.
+/// If a number is negative, i.e. it is less than zero, then sgn(x) = -1
+/// If a number is zero, then sgn(0) = 0
+/// If a number is positive, i.e. it is greater than zero, then sgn(x) = 1
+
+pub fn signum(number: f64) -> i8 {
+    if number == 0.0 {
+        return 0;
+    } else if number > 0.0 {
+        return 1;
+    }
+
+    -1
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn positive_integer() {
+        assert_eq!(signum(15.0), 1);
+    }
+
+    #[test]
+    fn negative_integer() {
+        assert_eq!(signum(-30.0), -1);
+    }
+
+    #[test]
+    fn zero() {
+        assert_eq!(signum(0.0), 0);
+    }
+}