// 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 const *)c)->b;
	if (b <= 0 || b == 1.0 || isnan(b) || isinf(b)) 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;
}