peek_top: Return the data element at the top of an rstack

In oneilsh/rstackdeque: Persistent Fast Amortized Stack and Queue Data Structures

Return the data element at the top of an rstack

Description

Simply returns the data element sitting at the top of the rstack, leaving the rstack alone.

Usage

peek_top(s, ...)

Arguments

s	rstack to peek at.
...	additional arguments to be passed to or from methods (ignored).

Details

Runs in O(1) worst-case time.

Value

data element existing at the top of the rstack.

See Also

without_top for removing the top element.

Examples

s <- rstack()
s <- insert_top(s, "a")
s <- insert_top(s, "b")
e <- peek_top(s)
print(e)
print(s)

## Assigning to the top data element with peek_top:
s <- rstack()
s <- insert_top(s, data.frame(a = 1, b = 1))
s <- insert_top(s, data.frame(a = 1, b = 1))

peek_top(s)$a <- 100
print(s)

peek_top(s) <- data.frame(a = 100, b = 100)

oneilsh/rstackdeque documentation built on May 17, 2022, 6:29 p.m.