1 files changed, 50 insertions, 0 deletions
diff --git a/lib/logarithm.c b/lib/logarithm.c
new file mode 100755
index 0000000..7451976
--- /dev/null
+++ b/lib/logarithm.c
@@ -0,0 +1,50 @@
+// Logarithm
+//
+// logarithm - log
+//
+// f( x ) = log_b( x )
+//
+// X_n - 1
+// Y_n - 1
+// C_n - 1
+//
+// c[0] = b
+
+
+#include <math.h>
+#include "ts.h"
+
+
+typedef struct {
+    fp_t b;
+} ts_logarithm_params_t;
+
+ts_parameter_t const ts_logarithm_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 1, .params_size = sizeof(ts_logarithm_params_t) };
+
+
+uint_t ts_logarithm_offset( ts_constant_t const *c )
+{
+	( void )c;
+	return ( 0 );
+}
+
+int ts_logarithm(
+	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_logarithm_p );
+	if ( !c ) return -1;
+	fp_t b = ((ts_logarithm_params_t *)c)->b;
+	if (b == 0 || b == 1.0) return -1;
+
+    b = _ts_reciprocal( log( b ) );
+
+	for( uint_t i = 0; i < n; ++i )
+	{
+		y[0][i] = x[0][i] > 0 ? log( x[0][i] ) * b : 0;
+	}
+	return 0;
+}
+