// Dawson Integral
//
// dawsn - Dawson function
//
// F(x) = e^(-x²) * ∫₀ˣ e^(t²) dt
//
// Inputs:    1
// Outputs:   1
// Constants: 0

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



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


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

int ts_dawsn(
	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_dawsn_p );
	(void)c;
	for( uint_t i = 0; i < n; ++i )
	{
		fp_t val = x[0][i];
		fp_t ax = fabs( val );
		fp_t y_val;

		if( ax < 3.0 )
		{
			fp_t t = ax;
			fp_t s = t;
			for( uint_t k = 1; k < 20; ++k )
			{
				t *= -2.0 * ax * ax / (fp_t)(2 * k + 1);
				s += t;
			}
			y_val = s;
		}
		else
		{
			y_val = 1.0 / ( 2.0 * ax + 1.0 / ( 2.0 * ax + 3.0 / ( 2.0 * ax + 5.0 / ( 2.0 * ax ) ) ) );
		}

		if( val < 0 )
			y_val = -y_val;

		y[0][i] = y_val;
	}
	return 0;
}