1 files changed, 12 insertions, 0 deletions
diff --git a/src/base/math/copysign.c b/src/base/math/copysign.c
new file mode 100644
index 0000000..0e7540b
--- /dev/null
+++ b/src/base/math/copysign.c
@@ -0,0 +1,12 @@
+#include <u.h>
+#include <base.h>
+
+double
+math·copysign(double x, double y)
+{
+	union {double f; uint64 i;} ux={x}, uy={y};
+	ux.i &= -1ULL/2;
+	ux.i |= uy.i & 1ULL<<63;
+
+	return ux.f;
+}