#define next_record repeat(record_length, _Right)
#define previous_record repeat(record_length, _Left)

#define to_end		next_record[next_record]
#define to_begin	previous_record[previous_record]

#define to_begin_of_carry \
	from(rail, to, carry) \
	to_begin \
	from(carry, to, rail)

#define to_end_of_carry \
	from(rail, to, carry) \
	to_end \
	from(carry, to, rail)

// Creating/expanding/shrinking rail

#define expand_rail(n) \
	next_record \
	plus(n) - \
	[[ next_record ]+[ previous_record ] next_record -]+ \
	previous_record

#define expand_n_clear_rail_(n) \
	next_record \
	plus(n) - \
	[[ next_record ]+ repeat(record_length, _Right clear) previous_record [ previous_record ] next_record -]+ \
	previous_record

//rail > 2
#define shrink_rail_(n) \
	next_record \
	plus(n) - \
	[[ next_record ] previous_record - previous_record [ previous_record ] next_record -]+ \
	previous_record

#define expand_n_clear_rail expand_n_clear_rail_(float_length)
#define shrink_rail shrink_rail_(float_length)

#define create_rail expand_rail(float_length)