#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define FROM   0.0
#define TO   100.0
#define STEP   0.01

#define INPUT  0.1
#define INITIAL_VALUE -10.0

#define sigmoid_slope -1.0

typedef struct {
    double output;
    double inner_state;
    double thres;
    double inp_wgt;
} neuron;


void initialize_neuron(neuron *a)
{
	a->output = 0.0;
	a->inner_state = INITIAL_VALUE;
	a->thres = 0.0;
	a->inp_wgt = 1.0;
}

double output_f(double value)
{
    return 1.0 / ( 1.0 + exp(sigmoid_slope * value) );
}

void update_neuron(neuron *a, double input)
{
	a->inner_state += (- a->output + a->inp_wgt * input - a->thres) * STEP;
	a->output = output_f(a->inner_state);
}

int main(int argc, char **argv)
{
	neuron a;
	double t;

  initialize_neuron(&a);

	t = FROM;
	while ( t <= TO ){
		update_neuron(&a, INPUT);
		printf("%f %f\n", t, a.output);
		t += STEP;
	}
	return EXIT_SUCCESS;
}