Appendix III

Appendix III – Code Samples

The following code fragments show how to implement these algorithms in languages like C. A slightly more general terminology has been used, for example the keyword "global" is introduced since in C the scope of a variable is defined by its position and this creates confusion when looking at code fragments. I have also replaced the specialised keywords "float" and "double" with "real".

The first code fragment shows how to convert a numerical Score between 0 and 1 to a traffic light representation:

/* Red, Yellow, Green and Score are reals */
global real Red, Yellow, Green;
/* convert Score to one or two traffic lights */
real indicate(real Score) {
/* check that Score is in valid range */
if (Score < 0 || Score > 1) return(-1);
if (Score < 0.5) {
Yellow = 2*Score;
Red = 1 – Yellow;
Green = 0;
} else {
Yellow = 2 - 2*Score;
Green = 1 – Yellow;
Red = 0;
}
return(Score);
}

The next code fragment shows how to integrate a set of N weighted Indicators or Characteristics. The individual memberships are stored in the arrays R[idx], Y[idx] and G[idx], and the weights are W[idx], where idx is an index that runs from 1 to N, and the integrated values are stored in R[0], Y[0] and G[0] (W[0] is used for the sum of weights, and should be 1 if the weights are normalised). The arrays are statically dimensioned to the largest value of N, Nmax, that is used.

global real R[Nmax], Y[Nmax], G[Nmax], W[Nmax];
/* combine and integrate indicator values */
void integrate (int N) {
/* initialise variables */
R[0] = 0;
Y[0] = 0;
G[0] = 0;
W[0] = 0;
int idx = 0;
/* run a loop from 1 to N */
while (idx++ < N) {
/* increment the storage counters */
R[0] += W[idx] * R[idx];
Y[0] += W[idx] * Y[idx];
G[0] += W[idx] * G[idx];
W[0] += W[idx];
}
/* divide the weighted sums by total weight */
R[0] /= W[0];
Y[0] /= W[0];
G[0] /= W[0];
return;
}

The final code fragments do defuzzification:

/* convert traffic lights to numeric score */
real defuzzify(real Red, Yellow, Green) {
return(0.5 * Yellow + Green);
}
/* calculate uncertainty in traffic lights */
real discord(real Red, Yellow, Green) {
return(4.0 * Red * Green);
}