listBuilder {crank}

Build a possibly nested list.

Description

Build a possibly nested list using the result of a function.

Usage

 listBuilder(x,FUN=NULL,fargs=NULL)

Arguments

x

The object that will be the first argument of ‘⁠FUN⁠’, or a possibly nested list of such objects.

FUN

A function that can accept ‘⁠x⁠’ as its first argument.

fargs

A list of the remaining arguments to ‘⁠FUN⁠’.

Details

‘⁠listBuilder⁠’ descends the list structure of ‘⁠x⁠’ if it is a list until it encounters a non-list element. It then passes that element as the first argument to ‘⁠FUN⁠’ and returns the value of ‘⁠FUN⁠’. This may be a list of elements, replacing the original element, hence the name.

Value

If ‘⁠x⁠’ is not a list and ‘⁠FUN⁠’ is NULL, ‘⁠x⁠’ is returned. If ‘⁠FUN⁠’ creates a list from one or more elements of ‘⁠x⁠’, a list or nested list will be returned. Successive calls to ‘⁠listBuilder⁠’ can rapidly create very large, deeply nested list structures.

Author(s)

Jim Lemon

See Also

list

Examples

 # define a function that splits a vector into a list
 splitvec<-function(x) {
  xlen<-length(x)
  if(xlen > 1) {
   newx<-vector("list",xlen)
   for(newlist in 1:xlen) newx[[newlist]]<-x[newlist]
   return(newx)
  }
  return(x)
 }
 testlist<-list(c(9,16),list(25,c(36,49)))
 listBuilder(testlist,splitvec)