Add signum function (#7526)

* Add signum function

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* Add typehints for functions

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update signum.py

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>

maths/signum.py

@@ -0,0 +1,34 @@
+"""
+Signum function -- https://en.wikipedia.org/wiki/Sign_function
+"""
+
+
+def signum(num: float) -> int:
+    """
+    Applies signum function on the number
+
+    >>> signum(-10)
+    -1
+    >>> signum(10)
+    1
+    >>> signum(0)
+    0
+    """
+    if num < 0:
+        return -1
+    return 1 if num else 0
+
+
+def test_signum() -> None:
+    """
+    Tests the signum function
+    """
+    assert signum(5) == 1
+    assert signum(-5) == -1
+    assert signum(0) == 0
+
+
+if __name__ == "__main__":
+    print(signum(12))
+    print(signum(-12))
+    print(signum(0))