Get the future of a future variable

Source: R/delayed_api-futureOf.R

Get the future of a future variable that has been created directly or indirectly via future().

futureOf(
  var = NULL,
  envir = parent.frame(),
  mustExist = TRUE,
  default = NA,
  drop = FALSE
)

Arguments

var

the variable. If NULL, all futures in the environment are returned.

envir

the environment where to search from.

mustExist

If TRUE and the variable does not exists, then an informative error is thrown, otherwise NA is returned.

default

the default value if future was not found.

drop

if TRUE and var is NULL, then returned list only contains futures, otherwise also default values.

Value

A Future (or default). If var is NULL, then a named list of Future:s are returned.

Examples

a %<-% { 1 }

f <- futureOf(a)
print(f)
#> SequentialFuture:
#> Label: <unnamed-12>
#> Expression:
#> {
#>     1
#> }
#> Globals: <none>
#> Packages: <none>
#> L'Ecuyer-CMRG RNG seed: <none> (seed = FALSE)
#> Capture standard output: TRUE
#> Capture condition classes: ‘condition’ (excluding ‘<none>’)
#> Immediate condition classes: ‘immediateCondition’
#> Lazy evaluation: FALSE
#> Local evaluation: TRUE
#> Asynchronous evaluation: TRUE
#> Early signaling: FALSE
#> Environment: 0x55e336958100
#> State: ‘finished’
#> Resolved: TRUE
#> Unique identifier: 39cc6c8a82f31b8f2757efa8ec95da26-12
#> Owner process: 39cc6c8a82f31b8f2757efa8ec95da26
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.00224185 secs (started 2025-06-30 20:21:26.147741)
#> Worker process: 39cc6c8a82f31b8f2757efa8ec95da26

b %<-% { 2 }

f <- futureOf(b)
print(f)
#> SequentialFuture:
#> Label: <unnamed-13>
#> Expression:
#> {
#>     2
#> }
#> Globals: <none>
#> Packages: <none>
#> L'Ecuyer-CMRG RNG seed: <none> (seed = FALSE)
#> Capture standard output: TRUE
#> Capture condition classes: ‘condition’ (excluding ‘<none>’)
#> Immediate condition classes: ‘immediateCondition’
#> Lazy evaluation: FALSE
#> Local evaluation: TRUE
#> Asynchronous evaluation: TRUE
#> Early signaling: FALSE
#> Environment: 0x55e336958100
#> State: ‘finished’
#> Resolved: TRUE
#> Unique identifier: 39cc6c8a82f31b8f2757efa8ec95da26-13
#> Owner process: 39cc6c8a82f31b8f2757efa8ec95da26
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.003289461 secs (started 2025-06-30 20:21:26.177253)
#> Worker process: 39cc6c8a82f31b8f2757efa8ec95da26

## All futures
fs <- futureOf()
print(fs)
#> $a
#> SequentialFuture:
#> Label: <unnamed-12>
#> Expression:
#> {
#>     1
#> }
#> Globals: <none>
#> Packages: <none>
#> L'Ecuyer-CMRG RNG seed: <none> (seed = FALSE)
#> Capture standard output: TRUE
#> Capture condition classes: ‘condition’ (excluding ‘<none>’)
#> Immediate condition classes: ‘immediateCondition’
#> Lazy evaluation: FALSE
#> Local evaluation: TRUE
#> Asynchronous evaluation: TRUE
#> Early signaling: FALSE
#> Environment: 0x55e336958100
#> State: ‘finished’
#> Resolved: TRUE
#> Unique identifier: 39cc6c8a82f31b8f2757efa8ec95da26-12
#> Owner process: 39cc6c8a82f31b8f2757efa8ec95da26
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.00224185 secs (started 2025-06-30 20:21:26.147741)
#> Worker process: 39cc6c8a82f31b8f2757efa8ec95da26
#> 
#> $b
#> SequentialFuture:
#> Label: <unnamed-13>
#> Expression:
#> {
#>     2
#> }
#> Globals: <none>
#> Packages: <none>
#> L'Ecuyer-CMRG RNG seed: <none> (seed = FALSE)
#> Capture standard output: TRUE
#> Capture condition classes: ‘condition’ (excluding ‘<none>’)
#> Immediate condition classes: ‘immediateCondition’
#> Lazy evaluation: FALSE
#> Local evaluation: TRUE
#> Asynchronous evaluation: TRUE
#> Early signaling: FALSE
#> Environment: 0x55e336958100
#> State: ‘finished’
#> Resolved: TRUE
#> Unique identifier: 39cc6c8a82f31b8f2757efa8ec95da26-13
#> Owner process: 39cc6c8a82f31b8f2757efa8ec95da26
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.003289461 secs (started 2025-06-30 20:21:26.177253)
#> Worker process: 39cc6c8a82f31b8f2757efa8ec95da26
#> 
#> $f
#> SequentialFuture:
#> Label: <unnamed-13>
#> Expression:
#> {
#>     2
#> }
#> Globals: <none>
#> Packages: <none>
#> L'Ecuyer-CMRG RNG seed: <none> (seed = FALSE)
#> Capture standard output: TRUE
#> Capture condition classes: ‘condition’ (excluding ‘<none>’)
#> Immediate condition classes: ‘immediateCondition’
#> Lazy evaluation: FALSE
#> Local evaluation: TRUE
#> Asynchronous evaluation: TRUE
#> Early signaling: FALSE
#> Environment: 0x55e336958100
#> State: ‘finished’
#> Resolved: TRUE
#> Unique identifier: 39cc6c8a82f31b8f2757efa8ec95da26-13
#> Owner process: 39cc6c8a82f31b8f2757efa8ec95da26
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.003289461 secs (started 2025-06-30 20:21:26.177253)
#> Worker process: 39cc6c8a82f31b8f2757efa8ec95da26
#> 


## Futures part of environment
env <- new.env()
env$c %<-% { 3 }

f <- futureOf(env$c)
print(f)
#> SequentialFuture:
#> Label: <unnamed-14>
#> Expression:
#> {
#>     3
#> }
#> Globals: <none>
#> Packages: <none>
#> L'Ecuyer-CMRG RNG seed: <none> (seed = FALSE)
#> Capture standard output: TRUE
#> Capture condition classes: ‘condition’ (excluding ‘<none>’)
#> Immediate condition classes: ‘immediateCondition’
#> Lazy evaluation: FALSE
#> Local evaluation: TRUE
#> Asynchronous evaluation: TRUE
#> Early signaling: FALSE
#> Environment: 0x55e336958100
#> State: ‘finished’
#> Resolved: TRUE
#> Unique identifier: 39cc6c8a82f31b8f2757efa8ec95da26-14
#> Owner process: 39cc6c8a82f31b8f2757efa8ec95da26
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.003133535 secs (started 2025-06-30 20:21:26.194197)
#> Worker process: 39cc6c8a82f31b8f2757efa8ec95da26

f2 <- futureOf(c, envir = env)
print(f2)
#> SequentialFuture:
#> Label: <unnamed-14>
#> Expression:
#> {
#>     3
#> }
#> Globals: <none>
#> Packages: <none>
#> L'Ecuyer-CMRG RNG seed: <none> (seed = FALSE)
#> Capture standard output: TRUE
#> Capture condition classes: ‘condition’ (excluding ‘<none>’)
#> Immediate condition classes: ‘immediateCondition’
#> Lazy evaluation: FALSE
#> Local evaluation: TRUE
#> Asynchronous evaluation: TRUE
#> Early signaling: FALSE
#> Environment: 0x55e336958100
#> State: ‘finished’
#> Resolved: TRUE
#> Unique identifier: 39cc6c8a82f31b8f2757efa8ec95da26-14
#> Owner process: 39cc6c8a82f31b8f2757efa8ec95da26
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.003133535 secs (started 2025-06-30 20:21:26.194197)
#> Worker process: 39cc6c8a82f31b8f2757efa8ec95da26

f3 <- futureOf("c", envir = env)
print(f3)
#> SequentialFuture:
#> Label: <unnamed-14>
#> Expression:
#> {
#>     3
#> }
#> Globals: <none>
#> Packages: <none>
#> L'Ecuyer-CMRG RNG seed: <none> (seed = FALSE)
#> Capture standard output: TRUE
#> Capture condition classes: ‘condition’ (excluding ‘<none>’)
#> Immediate condition classes: ‘immediateCondition’
#> Lazy evaluation: FALSE
#> Local evaluation: TRUE
#> Asynchronous evaluation: TRUE
#> Early signaling: FALSE
#> Environment: 0x55e336958100
#> State: ‘finished’
#> Resolved: TRUE
#> Unique identifier: 39cc6c8a82f31b8f2757efa8ec95da26-14
#> Owner process: 39cc6c8a82f31b8f2757efa8ec95da26
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.003133535 secs (started 2025-06-30 20:21:26.194197)
#> Worker process: 39cc6c8a82f31b8f2757efa8ec95da26

fs <- futureOf(envir = env)
print(fs)
#> $c
#> SequentialFuture:
#> Label: <unnamed-14>
#> Expression:
#> {
#>     3
#> }
#> Globals: <none>
#> Packages: <none>
#> L'Ecuyer-CMRG RNG seed: <none> (seed = FALSE)
#> Capture standard output: TRUE
#> Capture condition classes: ‘condition’ (excluding ‘<none>’)
#> Immediate condition classes: ‘immediateCondition’
#> Lazy evaluation: FALSE
#> Local evaluation: TRUE
#> Asynchronous evaluation: TRUE
#> Early signaling: FALSE
#> Environment: 0x55e336958100
#> State: ‘finished’
#> Resolved: TRUE
#> Unique identifier: 39cc6c8a82f31b8f2757efa8ec95da26-14
#> Owner process: 39cc6c8a82f31b8f2757efa8ec95da26
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.003133535 secs (started 2025-06-30 20:21:26.194197)
#> Worker process: 39cc6c8a82f31b8f2757efa8ec95da26
#>