1 files changed, 42 insertions, 0 deletions
diff --git a/lib/secant_inverse.c b/lib/secant_inverse.c
new file mode 100644
index 0000000..fbbab80
--- /dev/null
+++ b/lib/secant_inverse.c
@@ -0,0 +1,42 @@
+// Inverse Secant
+//
+// secant_inverse - asec
+//
+// f( x ) = asec( x )
+//        = acos( 1 / x )
+//
+// X_n - 1
+// Y_n - 1
+// C_n - 0
+
+
+#include <math.h>
+#include "ts.h"
+
+
+
+ts_parameter_t const ts_secant_inverse_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 0, .params_size = 0 };
+
+
+uint_t ts_secant_inverse_offset( ts_constant_t const *c )
+{
+	( void )c;
+	return ( 0 );
+}
+
+int ts_secant_inverse(
+	fp_t * const *y, uint_t y_n,
+	fp_t const * const *x, uint_t x_n,
+	uint_t n, ts_constant_t const *c
+)
+{
+	TS_PROLOGUE( ts_secant_inverse_p );
+	(void)c;
+	for( uint_t i = 0; i < n; ++i )
+	{
+		fp_t r = _ts_reciprocal( x[0][i] );
+		y[0][i] = ( r >= -1.0 && r <= 1.0 ) ? acos( r ) : 0;
+	}
+	return 0;
+}
+