Get evenly spaced numbers in a range, in C - c

Question

I am trying to perform an easy calculation without beeing able to figure out the right approach to it: I am trying to obtain a specific amount of N values, reading the step number from user input, within a certain range included between min and max also read from the user input. Those N values must be evenly spaced between themselves.
For instance, this should be able to produce a set of N numbers including the lower range limit and the upper one. I need to use decimal min and max and integer number of step.
This is the code I am trying to use:
#include <stdio.h>
int main()
{
double min;
double max;
int step;
double table_array[step];
table_array[0] = min;
printf("Enter the minimum value: ");
scanf("%lf", &min );
printf("Enter the maximum value: ");
scanf("%lf", &max );
printf("Enter the evenly spaced step value: ");
scanf("%d", &step );
printf("\n----------------------------------\n");
int i;
int increment;
for (i = 0; i <= step; i++){
increment = (max - min) / step;
table_array[i+1] = table_array[i] + increment;
while (table_array[i] < max){
printf("%i %lf\n",i, table_array[i]);
}
}
return 0;
}
I need to improve the for cycle for sure. Any suggestions? I assume it can be even totally wrong since it is not running, or better yet it is running but not showing the right result

Answer 1

First of all, you need declare an array with specific size. Initially the array size is not valid as step will initially have garbage value. then you are trying to print i with %i need to change that one with %d. with your step you need to calculate the increment only once. and as your increment can be double number then just make sure that you are using a double type for increment. now how i calculate the increment as 2 number must be min and max then there must be step >= 2 . suppose max =20 min =10 and step=3 so the numbers will be 10,15,20. so increment = (max -min )/(step-1) = 5. now make some complex case . if step = 1 then min must be equal to max. we need to check this case explicitly. another case if max < min then just need to swap them.
here is the code:
#include <stdio.h>
int
main ()
{
double min;
double max;
int step;
printf ("Enter the minimum value: ");
scanf ("%lf", &min);
printf ("Enter the maximum value: ");
scanf ("%lf", &max);
printf ("Enter the evenly spaced step value: ");
scanf ("%d", &step);
double table_array[step + 5];
table_array[0] = min;
printf ("\n----------------------------------\n");
int i;
double increment;
if (max < min){
double temp;
temp = min;
min = max;
max = temp;
}
if (step == 1 && max == min) {
i = 0;
printf ("%d %.18lf\n", i, table_array[i]);
} else {
increment = (max - min) / (step - 1);
i = 0;
printf ("%d %.18lf\n", i, table_array[i]);
for (i = 1; i < step; i++){
table_array[i] = table_array[i - 1] + increment;
printf ("%d %.18lf\n", i, table_array[i]);
}
}
return 0;
}

Answer 2

#include <stdio.h>
#define SWAPI(min,max,type) do{type tmp; if(min > max) {tmp = max; max = min; min = tmp;}}while(0)
double *getnumbers(double *table, size_t nelements, double max, double min)
{
double step;
if(table && nelements > 1 )
{
SWAPI(min,max, double);
step = (max - min) / (nelements - 1);
for(size_t element = 0; element < nelements; element++, min += step)
{
table[element] = min;
}
}
else
{
table = NULL;
}
return table;
}
void printtable(double *table, size_t num)
{
for(size_t i = 0; i < num; i++)
{
printf("[%zu] = %f\n", i, table[i]);
}
}
int main(int argc, char* argv[])
{
double numbers[25];
if(getnumbers(numbers,2,3,6)) printtable(numbers, 2);
printf("\n");
if(getnumbers(numbers,15,3,6)) printtable(numbers, 15);
}
https://godbolt.org/z/odscs6

Answer 3

#include <stdio.h> // printf, scanf, putchar
#include <float.h> // FLT_EPSILON
#include <math.h> // fabs
int isequal(double, double);
int main(void) {
double min, max, step, nnum;
printf("Maximum: "), scanf("%lf", &max); // Get maximum
printf("Minimum: "), scanf("%lf", &min); // Get minimum
if (min > max) { // If invalid maximum, handle error
puts("Maximum cannot be over minimum");
return 1; // Returning 1 indicates program failure
}
printf("Step: "), scanf("%lf", &step); // Get step
nnum = (max - min)/step;
if (!isequal(nnum, (int) nnum) || step <= 0) { // If invalid step, handle error
puts("Invalid step");
return 1;
}
putchar('\n'); // Separate input from output
for (int i = 0; i <= nnum; i++) {
printf("%d. %lf\n", i + 1, min);
min += step; // We already know it will go into maximum evenly
}
return 0; // Returning 0 indicates program success
}
int isequal(double x, double y) { // fabs() = Float absolute value
return fabs(x - y) < FLT_EPSILON; // FLT_EPSILON = Smallest comparable float value
}