inst/doc/priority-queues.R

In Immutables: Fast and Functional Data Structures

## ----setup, include = FALSE---------------------------------------------------
knitr::opts_chunk$set(collapse = TRUE, comment = "#>")
if(requireNamespace("pkgload", quietly = TRUE)) {
  pkgload::load_all(".", quiet = TRUE)
} else if(requireNamespace("Immutables", quietly = TRUE)) {
  library(Immutables)
} else {
  stop("Need either installed 'Immutables' or the 'pkgload' package to render this vignette.")
}

## -----------------------------------------------------------------------------
x <- priority_queue("task_a", "task_b", "task_c", priorities = c(3, 1, 2))
x

peek_min(x)
res <- pop_max(x)

res$value
res$priority
res$remaining

## -----------------------------------------------------------------------------
q <- as_priority_queue(letters[1:4], priorities = c(3, 1, 2, 1))
q

## -----------------------------------------------------------------------------
y <- priority_queue() |>
  insert("Jones", priority = "B") |>
  insert("Smith", priority = "A") |>
  insert("Adams", priority = "A")

peek_min(y)
peek_all_min(y)

res1 <- pop_min(y)
res1$value
res1$priority
res1$remaining

res2 <- pop_all_min(y)

res2$elements
res2$remaining

## -----------------------------------------------------------------------------
as.list(res2$elements) |> str()
as.list(res2$elements, drop_meta = TRUE) |> str()

## -----------------------------------------------------------------------------
empty_q <- priority_queue()
length(empty_q)
peek_min(empty_q)
pop_min(empty_q)

## -----------------------------------------------------------------------------
q <- priority_queue("a", "b", "c", priorities = c(3, 1, 2))
min_priority(q)
max_priority(q)
min_priority(priority_queue())  # NULL when empty

## -----------------------------------------------------------------------------
q <- priority_queue(a = "task-a", b = "task-b", priorities = c(2, 1)) |>
  insert("task-c", priority = 3, name = "c")

q[["b"]]
q[c("a", "c")]

try(q[1])         # positional indexing blocked
try(q$a <- "!!")  # replacement blocked

## -----------------------------------------------------------------------------
q <- priority_queue("alice", "bob", "carol", priorities = c(3, 1, 2))
fapply(q, function(value, priority) toupper(value))

## -----------------------------------------------------------------------------
q <- priority_queue("task_a", "task_b", "task_c", priorities = c(3, 1, 2))
loop(for (v in q) print(v))

## -----------------------------------------------------------------------------
a <- priority_queue("x", "y", priorities = c(5, 1))
b <- priority_queue("z", priorities = 3)
m <- merge(a, b)
length(m)
peek_min(m)
peek_max(m)

## -----------------------------------------------------------------------------
y <- priority_queue() |>
  insert("Jones", priority = "B") |>
  insert("Smith", priority = "A") |>
  insert("Adams", priority = "A")

as_flexseq(y)
as_flexseq(as.list(y))