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Primitive If

Source: R/primitives.R
prim_if.Rd

Conditional execution of one of two branches based on a scalar boolean predicate, mirroring R's if construct: it branches between two functions and evaluates only the selected one. Its arguments are named after that construct, where prim_ifelse() – which selects element-wise between two arrays – is named after ifelse().

Usage

prim_if(pred, true, false)

Arguments

pred

(arrayish)
Predicate deciding which branch to execute. Must be a scalar of the boolean data type, or an R logical.

true, false

(function())
Zero-argument functions for the true and false branches. Both must return outputs of the same structure, data types and shapes. As with prim_ifelse(), whose two values must already agree, nothing is promoted: branches that disagree are an error.

Value

(arrayish | list)
Result of the executed branch: an array, or a tree of them in the sense of pjrt's RTree – a list, nested arbitrarily – with the structure, data types and shapes both branches share.

Implemented Rules

  • stablehlo

  • quickr

  • reverse

StableHLO

Lowers to hlo_if(), specified under if.

See also

nv_if(), prim_ifelse()

Examples

# both branches must return the same structure, data types and shapes
prim_if(nv_scalar(TRUE), \() nv_scalar(1), \() nv_scalar(2))
#> AnvlArray
#>  1
#> [ CPUf32{} ]