Made gcd a free function

Author: NevinBR

Sources/IntegerUtilities/GCD.swift

@@ -9,39 +9,36 @@
 //
 //===----------------------------------------------------------------------===//
 
-extension BinaryInteger {
+/// The greatest common divisor of `a` and `b`.
+///
+/// If both inputs are zero, the result is zero. If one input is zero, the
+/// result is the absolute value of the other input.
+///
+/// [wiki]: https://en.wikipedia.org/wiki/Greatest_common_divisor
+@inlinable
+public func gcd<T: BinaryInteger>(_ a: T, _ b: T) -> T {
+  var x = a.magnitude
+  var y = b.magnitude
 
-  /// The greatest common divisor of `a` and `b`.
-  ///
-  /// If both inputs are zero, the result is zero. If one input is zero, the
-  /// result is the absolute value of the other input.
-  ///
-  /// [wiki]: https://en.wikipedia.org/wiki/Greatest_common_divisor
-  @inlinable
-  public static func gcd(_ a: Self, _ b: Self) -> Self {
-    var x = a.magnitude
-    var y = b.magnitude
-    
-    if x == 0 { return Self(y) }
-    if y == 0 { return Self(x) }
-    
-    let xtz = x.trailingZeroBitCount
-    let ytz = y.trailingZeroBitCount
-    
-    x >>= xtz
-    y >>= ytz
-    
-    // The binary GCD algorithm
-    //
-    // At the top of the loop both x and y are odd. Each pass removes at least
-    // one low-order bit from the larger of the two, so the number of iterations
-    // is bounded by the sum of the bit-widths of the inputs.
-    while x != 0 {
-      if x < y { swap(&x, &y) }
-      x -= y
-      x >>= x.trailingZeroBitCount
-    }
-    
-    return Self(y << min(xtz, ytz))
+  if x == 0 { return T(y) }
+  if y == 0 { return T(x) }
+  
+  let xtz = x.trailingZeroBitCount
+  let ytz = y.trailingZeroBitCount
+  
+  x >>= xtz
+  y >>= ytz
+  
+  // The binary GCD algorithm
+  //
+  // At the top of the loop both x and y are odd. Each pass removes at least
+  // one low-order bit from the larger of the two, so the number of iterations
+  // is bounded by the sum of the bit-widths of the inputs.
+  while x != 0 {
+    if x < y { swap(&x, &y) }
+    x -= y
+    x >>= x.trailingZeroBitCount
   }
+  
+  return T(y << min(xtz, ytz))
 }