lib/atanh.c


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// Hyperbolic Arctangent
//
// atanh - inverse hyperbolic tangent
//
// y[t] = atanh( x[t] )       if |x[t]| < 1
// y[t] = +INFINITY           if x[t] == 1
// y[t] = -INFINITY           if x[t] == -1
// y[t] = NAN                 if |x[t]| > 1
//
// X_n - 1
// Y_n - 1
// C_n - 0

#include <math.h>
#include "ts.h"


ts_parameter_t const ts_atanh_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 0, .params_size = 0 };


uint_t ts_atanh_offset( ts_constant_t const *c )
{
	( void )c;
	return ( 0 );
}

int ts_atanh(
	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_atanh_p );
	(void)c;
	for( uint_t i = 0; i < n; ++i )
	{
		fp_t v = x[0][i];
		if ( v > -1.0 && v < 1.0 )
			y[0][i] = atanh( v );
		else if ( v == 1.0 )
			y[0][i] = INFINITY;
		else if ( v == -1.0 )
			y[0][i] = -INFINITY;
		else
			y[0][i] = (fp_t)NAN;
	}
	return 0;
}