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The Learning Brick Sorter • Masterpiece 2 91

the Learning Brick Sorter adaptable to different situations.Thus, we won’t store any asso-
ciations between the colors and the bins, but we also won’t store any values to define
those colors.This way the Learning Brick Sorter will work with a set of any three colors,
provided that their readings are well separated.
A “color” (actually the amount of light reflected by that color) can be stored into a
single variable, but I find this approach a bit risky. If the user places the bricks at slightly
different distances from the light sensor, the same color can result in different readings.
For this reason, I chose to define colors using a range bounded by a lower and an upper
limit.The Learning Brick Sorter has three bins, thus we need three ranges for three dif-
ferent colors:

#define RANGES 3
int min[RANGES]; // lower limits of the ranges
int max[RANGES]; // upper limits of the ranges

NOTE
You don’t need to type any code, because you’ll find the complete program
included in the companion disk of this book.

To handle these ranges, we need an additional variable that tracks how many of them
have been used:
int top_range; // highest used range index

Initially top_range is set to –1, meaning that no range has been used yet. When a
reading arrives, we scan the ranges from 0 to top_range, to see whether the value falls
inside one of the defined ranges. If it does, this means the color belongs to that of the
specified range, otherwise we increment top_range by one and define a new range.
light_value = SENSOR_1;
// search if the light value is contained in
// one of the already defined ranges
for(range=0;range<=top_range;range++) {
if (light_value>=min[range] && light_value<=max[range]) break;
}

// if not, define a new range
if (range>top_range) {
top_range++;
// if all ranges have been used, beep for error and terminate program
if (top_range>=RANGES) {