Back - Function Summary
Returns the series at its previous position.
series - The series argument. (must be: series port)
If the series is at its head, it will remain at its
head. BACK will not go past the head, nor will it wrap
to the tail.
str: tail "time"
str: back str
blk: tail [1 2 3 4]
blk: back blk
print first blk
head - Returns the series at its head.
head? - Returns TRUE if a series is at its head.
last - Returns the last value of a series.
next - Returns the series at its next position.
tail - Returns the series at the position after the last value.
tail? - Returns TRUE if a series is at its tail.