1 files changed, 60 insertions, 1 deletions
diff --git a/src/complex/cacos.c b/src/complex/cacos.c
index b669f478..3bfe9d38 100644
--- a/src/complex/cacos.c
+++ b/src/complex/cacos.c
@@ -1,10 +1,69 @@
 # define TGSOURCE "../complex/cacos.c"
 #include "_tgmath.h"
-
 #include <complex.h>
+#include "math.h"
+#include "fenv.h"
+
+#include "../math/M_PI.c"
+#include "../math/M_PI_2.c"
+#include "../math/M_PI_4.c"
 
 TYPE complex TGFN(cacos)(TYPE complex z)
 {
+	int classr = fpclassify(TGFN(creal)(z));
+	int classi = fpclassify(TGFN(cimag)(z));
+	int signr = signbit(TGFN(creal)(z));
+	int signi = signbit(TGFN(cimag)(z));
+
+	if (classr == FP_ZERO && classi == FP_ZERO) {
+		return TGCMPLX(M_PI_2, 0.0);
+	}
+
+	if (classr == FP_ZERO && classi == FP_NAN) {
+		return TGCMPLX(M_PI_2, NAN);
+	}
+
+	if (classr != FP_INFINITE && classi == FP_INFINITE) {
+		return TGCMPLX(M_PI_2, INFINITY);
+	}
+
+	if (classr != FP_ZERO && classr != FP_INFINITE && classi == FP_NAN) {
+		return TGCMPLX(NAN, NAN);
+	}
+
+	if (classr == FP_INFINITE && signr && classi != FP_INFINITE && !signi) {
+		return TGCMPLX(M_PI, -INFINITY);
+	}
+
+	if (classr == FP_INFINITE && !signr && classi != FP_INFINITE && !signi) {
+		return TGCMPLX(0.0, -INFINITY);
+	}
+
+	if (classr == FP_INFINITE && signr && classi == FP_INFINITE) {
+		return TGCMPLX(3 * M_PI_4, -INFINITY);
+	}
+
+	if (classr == FP_INFINITE && !signr && classi == FP_INFINITE) {
+		return TGCMPLX(M_PI_4, -INFINITY);
+	}
+
+	if (classr == FP_INFINITE && classi == FP_NAN) {
+		return TGCMPLX(NAN, INFINITY);
+	}
+
+	if (classr == FP_NAN && classi != FP_INFINITE) {
+		feraiseexcept(FE_INVALID);
+		return TGCMPLX(NAN, NAN);
+	}
+
+	if (classr == NAN && classi == FP_INFINITE) {
+		return TGCMPLX(NAN, -INFINITY);
+	}
+
+	if (classr == NAN && classi == NAN) {
+		return TGCMPLX(NAN, NAN);
+	}
+
 	return z;
 }