Define consecutive values

resistor_color.h

#ifndef RESISTOR_COLOR_H
#define RESISTOR_COLOR_H
#include <stdint.h>

#define COLORS                                                                 \
   BLACK, BROWN, RED, ORANGE, YELLOW, GREEN, BLUE, VIOLET, GREY, WHITE

typedef enum RESISTOR_BANDS { COLORS } resistor_band_t;

uint16_t color_code(resistor_band_t color);
resistor_band_t *colors(void);

#endif

resistor_color.c

#include "resistor_color.h"

static resistor_band_t color_array[10] = { COLORS };

resistor_band_t *colors(void)
{
   return color_array;
}

uint16_t color_code(resistor_band_t color)
{
   return color;
}

The header file starts by using the #define directive to set the consectuve values. After the COLORS symbol is a line continuation character. Since the COLORS symbol is not followed by a single value but by a series of comma-separated symbols, each of those symbols is given a default value, starting with 0. The COLORS symbol expands to that series of values. The line continuation character is used only because the length of the series of values would make the line exceed 80 characters.

The COLORS values are passed into a typedef. The typedef uses the series of COLORS values to create the new enum type of resistor_band_t.

In the source file, the same series of COLORS values is used to initialize the color_array.

The colors function returns the color_array.

The color_code function returns the resistor_band_t value passed in, since its underlying value is an int with the expected value.