futureverse.org/demo.qmd at master · futureverse/futureverse.org · GitHub

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---
title: Try Futureverse in the Browser
format: live-html
engine: knitr
webr:
  repos:
    - https://cran.r-universe.dev
  packages:
    - future
    - futurize
    - future.apply
    - purrr
    - furrr
    - foreach
    - doFuture
  cell-options:
    echo: true
    persist: true
---

You can try the future ecosystem in the below R WebAssembly ("[webR]") widget. The "only" thing is that WebAssembly does _not_ support parallel processing, so everything will run sequentially. Also, the widget buffers all output until everything has finished running.

::: {.panel-tabset}

## **futurize** 💫

_The `futurize()` function rewrites the expression to use the corresponding **future.apply**, **furrr**, and **doFuture** expression. It is part of the **[futurize]** package released in January 2026._

```{webr}
library(futurize)
plan(multisession)

slow_fcn <- function(x) {
  message("x = ", x)
  x^2
}

X <- 1:3

message("Evaluate it in parallel in the background")
f <- future(slow_fcn(X[1]))
y <- value(f)
print(y)

message("Futurized version of base R apply")
y <- lapply(X, slow_fcn) |> futurize()
str(y)

message("Futurized version of purrr map")
library(purrr)
y <- X |> map(slow_fcn) |> futurize()
str(y)

message("Futurized version of foreach")
library(foreach)
y <- foreach(x = X) %do% slow_fcn(x) |> futurize()
str(y)
```

## Pre-**futurize**

```{webr}
library(future)
plan(multisession)

slow_fcn <- function(x) {
  message("x = ", x)
  x^2
}

X <- 1:3

message("Evaluate it in parallel in the background")
f <- future(slow_fcn(X[1]))
y <- value(f)
print(y)

message("Futurized version of base R apply via future.apply")
library(future.apply)
y <- future_lapply(X, slow_fcn)
str(y)

message("Futurized version of purrr via furrr")
library(furrr)
y <- X |> future_map(slow_fcn)
str(y)

message("Futurized version of foreach via doFuture (modern)")
library(foreach)
library(doFuture)
y <- foreach(x = X) %dofuture% slow_fcn(x)
str(y)

message("Futurized version of foreach via doFuture (traditional)")
library(foreach)
doFuture::registerDoFuture()
y <- foreach(x = X) %dopar% slow_fcn(x)
str(y)
```

:::

[webR]: https://github.com/r-wasm/webr/
[futurize]: https://futurize.futureverse.org