// gcc - gbu c  will not allow calc in const initializer - but OK in define
#define FEET_PER_METER 3.28
#define METER_PER_FOOT (1.0 / FEET_PER_METER)
#define FEET_PER_MILE 5280.0
#define METERS_PER_KILOMETER 1000.0
#define MILES_PER_FOOT (1.0 / FEET_PER_MILE)
#define MILES_PER_KILOMETER (MILES_PER_FOOT * FEET_PER_METER * METERS_PER_KILOMETER) 

/* another sort of comment */
const double feet_per_meter = FEET_PER_METER;
const double meter_per_foot = METER_PER_FOOT;
const double feet_per_mile = FEET_PER_MILE;
const double meters_per_kilometer = METERS_PER_KILOMETER;
const double miles_per_foot = MILES_PER_FOOT;
const double miles_per_kilometer = MILES_PER_KILOMETER;