Have a look at the first element from an object without removing it

Source: R/methods_peek.R, R/ds_deque.R, R/ds_heap.R, and 1 more

Peeks into an object, i.e. takes the first element and returns it without removing it from the object. The data structure that has a peek method usually uses some sort of priority of its elements.

peek(obj)

# S4 method for deque
peek(obj)

# S4 method for heap
peek(obj)

# S4 method for map
peek(obj)

Arguments

obj

the object to peek

Value

returns the first element from obj as list

Examples


 # peeks into a queue
 q <- queue()
 q <- insert(q, list(environment(), data.frame(a=1)))
 peek(q)
#> <environment: 0x558eb1a904a8>

 # peeks into a fibonacci heap
 b_heap <- binomial_heap()
 b_heap <- insert(b_heap, letters[seq(3)], list(1, diag(3), rnorm(2)))
 peek(b_heap)
#> $a
#> [1] 1
#> 

 # peeks into a \code{hashmap}
 h_map <- hashmap()
 h_map[letters] <- rnorm(length(letters))
 peek(h_map)
#> $t
#> [1] 0.4861489
#> 
#> $w
#> [1] 0.9463479
#> 
#> $x
#> [1] 1.316826
#> 
#> $y
#> [1] -0.29664
#> 
#> $z
#> [1] -0.3872136
#> 

 # peeks into a \code{bimap}
 b_map <- bimap("integer", "integer")
 b_map[seq(10)] <- seq(10, 1)
 peek(b_map)
#> $`1`
#> [1] 10
#> 
#> $`2`
#> [1] 9
#> 
#> $`3`
#> [1] 8
#> 
#> $`4`
#> [1] 7
#> 
#> $`5`
#> [1] 6
#>