1 files changed, 51 insertions, 0 deletions
diff --git a/src/math/sin.c b/src/math/sin.c
new file mode 100644
index 00000000..c5d127f0
--- /dev/null
+++ b/src/math/sin.c
@@ -0,0 +1,51 @@
+# define TGSOURCE "sin.c"
+#include <math.h>
+#include "nonstd/tgmath.h"
+#include "errno.h"
+
+/** sine **/
+TYPE TGFN(sin)(TYPE x)
+{
+	int MAXLOOPS = 10;
+	int factorial = 1;
+	int i;
+	TYPE sine = 0.0;
+	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 input domain */
+	/* TODO: tweak the max number of loops */
+
+	/* RETURN_SUCCESS(the sine of ARGUMENT(x)); */
+
+	/* sin x = x - x^3/3! + x^5/5! - x^7/7! ... */
+	for (i = 1; i < MAXLOOPS; i++) {
+		power = power * x;
+		factorial = factorial * i;
+
+		if (i % 4 == 1) {
+			sine += power / factorial;
+		} else if (i % 4 == 3) {
+			sine -= power / factorial;
+		}
+	}
+
+	return sine;
+}
+
+/***
+compute sine of ARGUMENT(x), in radians.
+***/
+
+/*
+IMPLEMENTATION(The value returned on a domain error, CONSTANT(HUGE_VAL))
+LINK(m)
+*/
+/*
+STDC(1)
+*/