1 files changed, 43 insertions, 0 deletions
diff --git a/lib/tangent_hyperbolic_inverse.c b/lib/tangent_hyperbolic_inverse.c
new file mode 100644
index 0000000..1c337ba
--- /dev/null
+++ b/lib/tangent_hyperbolic_inverse.c
@@ -0,0 +1,43 @@
+// Inverse Hyperbolic Tangent
+//
+// tangent_hyperbolic_inverse - atanh
+//
+// f( x ) = atanh( x )
+//        = 0.5 * ln( ( 1 + x ) / ( 1 - x ) )    |x| < 1
+//
+// X_n - 1
+// Y_n - 1
+// C_n - 0
+
+
+#include <math.h>
+#include "ts.h"
+
+
+
+ts_parameter_t const ts_tangent_hyperbolic_inverse_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 0, .params_size = 0 };
+
+
+uint_t ts_tangent_hyperbolic_inverse_offset( ts_constant_t const *c )
+{
+	( void )c;
+	return ( 0 );
+}
+
+int ts_tangent_hyperbolic_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_tangent_hyperbolic_inverse_p );
+	(void)c;
+	for( uint_t i = 0; i < n; ++i )
+	{
+		fp_t xv = x[0][i];
+		if( fabs(xv) >= 1.0 ) { y[0][i] = 0; continue; }
+		y[0][i] = atanh( xv );
+	}
+	return 0;
+}
+