gsl_histogram *gsl_hist;
};
-struct histogram * histogram_create (int bins, double max, double min);
+/*
+ Prepare a histogram for data which lies in the range [min, max)
+ bin_width is a nominal figure only. It is a hint about what might be
+ an good approximate bin width, but the implementation will adjust it
+ as it thinks fit.
+ */
+struct histogram * histogram_create (double bin_width, double min, double max);
void histogram_add (struct histogram *h, double y, double c);