2023-2-WS_group_project_Linkes-Twix/src/logarithmus.c

#include <stdio.h>
#include <limits.h>

#include "logarithmus.h"
#include "exponent.h"

double logX(double base, double value){
    if(base == 1.0 || base <= 0.0 || value <= 0.0){
        return -1.0;
    }
    return(logN(value)/logN(base));
}

double log10(double value){
    return logX(10.0, value);
}

double log2(double value){
    return logX(2.0, value);
}
double lns(double x, double eps){
    double yn = x - 1.0;
    double yn1 = yn;

    do{
        yn = yn1;
        yn1 = yn + 2 * (x - exponential(yn)) / (x + exponential(yn));
    } while (absD(yn - yn1) > eps);

    return yn1;
}

double lnb(double x){
    int power_adjust = 0;
    while (x > 1.0) {
        x /= exponential(1);
        power_adjust++;
    }
    while (x < .25) {
        x *= exponential(1);
        power_adjust--;
    }
    
    x -= 1.0;
    double t = 0.0, s = 1.0, z = x;
    for (int k=1; k<=100; k++) {
        t += z * s / k;
        z *= x;
        s = -s;
    }
    return t + power_adjust;   
}

double logN(double x){
    if(x <= 0){
        return -1.0;
    }
    if(x<200){
        return lns(x, 0.00000001);
    }
    else{
        return lnb(x);
    }    
}