While Loop

Executes a functional while loop.

Usage

nv_while(init, cond, body)

Arguments

init

(named list())
Named list of initial state values, a tree in the sense of pjrt's RTree. Each leaf becomes a parameter of the loop's sub-graphs. R values are materialized at their default data type.

cond

(function)
Condition function returning a scalar boolean. Receives the state values as arguments.

body

(function)
Body function returning the updated state as a named list with the same structure, data types and shapes as init. Nothing is promoted: a loop-carried state is meant to be heterogeneous, so each member keeps its own data type across iterations.

Value

(named list)
A tree of the loop-carried arrays – see RTree – in its final state after the loop terminates, with init's structure, data types and shapes.

See also

prim_while() for the underlying primitive.

Examples

# the loop state is a named list, and each member keeps its data type
nv_while(
  init = list(i = nv_scalar(0L), total = nv_scalar(0L)),
  cond = function(i, total) i < 5L,
  body = function(i, total) list(
    i = i + 1L,
    total = total + i
  )
)
#> $i
#> AnvlArray
#>  5
#> [ CPUi32{} ] 
#> 
#> $total
#> AnvlArray
#>  10
#> [ CPUi32{} ] 
#>