You can take relative weights (a,b,c) and take the partial sums: (0,a,a+b,a+b+c) random() gives values in [0,1], so divide your numbers by a + b + c. Generat

You can take relative weights (a,b,c) and take the partial sums: (0,a,a+b,a+b+c) random() gives values in [0,1], so divide your numbers by a + b + c. Generating random structures is the tip of a very big iceberg.