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library(rlang)
library(pryr)

# ===========================
# Normal quosures
# ===========================
# as_function() with a quosure: OK
a <- 1
x <- quo(a + 10)
a <- 2

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library(digest)
library(promises)
library(cache)

# Given a list with items named `value` and `visible`, return `x$value` either
# visibly, or invisibly, depending on the value of `x$visible`.
valueWithVisible <- function(x) {
  if (x$visible) x$value else invisible(x$value)
}

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library(profvis)
library(microbenchmark)
library(memoise)
library(digest)

# Bare function
f <- function(a, b) {
  a + b
}

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library(httpuv)

# Create a web server app which returns the time and prints out the value of
# a header named "test-header".
handle_request <- function(req) {
  list(
    status = 200L,
    headers = list('Content-Type' = 'text/plain'),
    body = paste0(
      "The time is: ", Sys.time(), "\n",

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> install.packages("Rcpp")
Installing package into ‘/Users/winston/R/3.6’
(as ‘lib’ is unspecified)
trying URL 'https://cloud.r-project.org/bin/macosx/el-capitan/contrib/3.6/Rcpp_1.0.4.tgz'
Content type 'application/x-gzip' length 3124401 bytes (3.0 MB)
==================================================
downloaded 3.0 MB


The downloaded binary packages are in

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This is an example of C code calling an R function, by building a function call and then evaluating it.

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# First, need to install crandb
# devtools::install_github('r-hub/crandb')

# Memoize crandb::package because we end up making a lot of repetitive calls.
package <- memoise::memoise(crandb::package)

# Get a list of built-in packages. We don't need to check the version
# information for these packages.
builtin_pkgs <- memoise::memoise(function() {
  pkgs <- installed.packages()

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library(httpuv)

PORT <- 7000

app <- list(
  call = function(req) {
    page(req)
  },
  onWSOpen = function(ws) {
    ws$onMessage(function(binary, message) {

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## Modifying a vector in a parent environment

## This tests whether it's faster to use `self` or not, and whether it's faster to use `<-` vs `<<-`.

foo <- local({
  x <- integer()
  self <- environment()
  
  # Four different ways of setting a value:
  #  * With and without using `self`

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# get_symbols() returns all symbols that are registered in R's symbol table.
#
# new_symbols() returns all symbols that have been added since the last time
# new_symbols() was run. If you want to test whether your code causes the symbol
# table to grow, run new_symbols(), then run your code, then run new_symbols()
# again.

get_symbols <- inline::cfunction(
  includes = "
    #define HSIZE   49157 /* The size of the hash table for symbols */