1 files changed, 51 insertions, 0 deletions
diff --git a/src/math/cos.c b/src/math/cos.c
new file mode 100644
index 00000000..0690b6ee
--- /dev/null
+++ b/src/math/cos.c
@@ -0,0 +1,51 @@
+# define TGSOURCE "cos.c"
+#include <math.h>
+#include "nonstd/tgmath.h"
+#include "errno.h"
+
+/** cosine **/
+TYPE TGFN(cos)(TYPE x)
+{
+	int MAXLOOPS = 10;
+	int factorial = 1;
+	int i;
+	TYPE cosine = 1.0;
+	TYPE power = 1.0;
+
+	if (0) {
+		errno = ERANGE; /* The result cannot be represented */
+		/* RETURN_FAILURE(CONSTANT(HUGE_VAL), A range error occurred); */
+		return TGHUGE;
+	}
+
+	/* TODO: make sure x is in the right domain */
+	/* TODO: tweak number of loops */
+
+	/* cos x = 1 - x^2/2! + x^4/4! -x^6/6! ... */
+	for (i = 1; i < MAXLOOPS; i++) {
+		power = power * x;
+		factorial = factorial * i;
+
+		if (i % 4 == 0) {
+			cosine += power / factorial;
+		} else if (i % 4 == 2) {
+			cosine -= power / factorial;
+		}
+	}
+
+	/* RETURN_SUCCESS(the cosine of ARGUMENT(x)); */
+	return cosine;
+}
+
+/***
+compute cosine of ARGUMENT(x), in radians.
+***/
+
+/*
+IMPLEMENTATION(The value returned on a domain error, CONSTANT(HUGE_VAL))
+LINK(m)
+*/
+/*
+STDC(1)
+*/
+