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Get the future of a future variable

Source: R/delayed_api-futureOf.R
futureOf.Rd

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

Usage

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 exist, then an informative error is thrown, otherwise default 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 is 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
#> Early signaling: FALSE
#> Actions: [n=1] ‘run’
#> State: ‘finished’ ("Future was resolved successfully")
#> Resolved: TRUE
#> Unique identifier: d7f52821a764cc4117f3269bee73e7c7-12
#> Owner process: d7f52821a764cc4117f3269bee73e7c7
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.001897573 secs (started 2026-04-28 21:54:44.591214)
#> Worker process: d7f52821a764cc4117f3269bee73e7c7

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
#> Early signaling: FALSE
#> Actions: [n=1] ‘run’
#> State: ‘finished’ ("Future was resolved successfully")
#> Resolved: TRUE
#> Unique identifier: d7f52821a764cc4117f3269bee73e7c7-13
#> Owner process: d7f52821a764cc4117f3269bee73e7c7
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.001755714 secs (started 2026-04-28 21:54:44.59811)
#> Worker process: d7f52821a764cc4117f3269bee73e7c7

## 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
#> Early signaling: FALSE
#> Actions: [n=1] ‘run’
#> State: ‘finished’ ("Future was resolved successfully")
#> Resolved: TRUE
#> Unique identifier: d7f52821a764cc4117f3269bee73e7c7-12
#> Owner process: d7f52821a764cc4117f3269bee73e7c7
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.001897573 secs (started 2026-04-28 21:54:44.591214)
#> Worker process: d7f52821a764cc4117f3269bee73e7c7
#> 
#> $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
#> Early signaling: FALSE
#> Actions: [n=1] ‘run’
#> State: ‘finished’ ("Future was resolved successfully")
#> Resolved: TRUE
#> Unique identifier: d7f52821a764cc4117f3269bee73e7c7-13
#> Owner process: d7f52821a764cc4117f3269bee73e7c7
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.001755714 secs (started 2026-04-28 21:54:44.59811)
#> Worker process: d7f52821a764cc4117f3269bee73e7c7
#> 
#> $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
#> Early signaling: FALSE
#> Actions: [n=1] ‘run’
#> State: ‘finished’ ("Future was resolved successfully")
#> Resolved: TRUE
#> Unique identifier: d7f52821a764cc4117f3269bee73e7c7-13
#> Owner process: d7f52821a764cc4117f3269bee73e7c7
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.001755714 secs (started 2026-04-28 21:54:44.59811)
#> Worker process: d7f52821a764cc4117f3269bee73e7c7
#> 


## 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
#> Early signaling: FALSE
#> Actions: [n=1] ‘run’
#> State: ‘finished’ ("Future was resolved successfully")
#> Resolved: TRUE
#> Unique identifier: d7f52821a764cc4117f3269bee73e7c7-14
#> Owner process: d7f52821a764cc4117f3269bee73e7c7
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.001839876 secs (started 2026-04-28 21:54:44.60639)
#> Worker process: d7f52821a764cc4117f3269bee73e7c7

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
#> Early signaling: FALSE
#> Actions: [n=1] ‘run’
#> State: ‘finished’ ("Future was resolved successfully")
#> Resolved: TRUE
#> Unique identifier: d7f52821a764cc4117f3269bee73e7c7-14
#> Owner process: d7f52821a764cc4117f3269bee73e7c7
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.001839876 secs (started 2026-04-28 21:54:44.60639)
#> Worker process: d7f52821a764cc4117f3269bee73e7c7

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
#> Early signaling: FALSE
#> Actions: [n=1] ‘run’
#> State: ‘finished’ ("Future was resolved successfully")
#> Resolved: TRUE
#> Unique identifier: d7f52821a764cc4117f3269bee73e7c7-14
#> Owner process: d7f52821a764cc4117f3269bee73e7c7
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.001839876 secs (started 2026-04-28 21:54:44.60639)
#> Worker process: d7f52821a764cc4117f3269bee73e7c7

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
#> Early signaling: FALSE
#> Actions: [n=1] ‘run’
#> State: ‘finished’ ("Future was resolved successfully")
#> Resolved: TRUE
#> Unique identifier: d7f52821a764cc4117f3269bee73e7c7-14
#> Owner process: d7f52821a764cc4117f3269bee73e7c7
#> Class: ‘SequentialFuture’, ‘UniprocessFuture’, ‘Future’
#> Value: 39 bytes of class ‘numeric’
#> Duration: 0.001839876 secs (started 2026-04-28 21:54:44.60639)
#> Worker process: d7f52821a764cc4117f3269bee73e7c7
#>