nullperm {permutations}

Null permutations

Description

Null permutations are the equivalent of NULL

Usage

nullcycle
nullword

Format

Object nullcycle is an empty list coerced to class cycle, specifically cycle(list())

Object nullword is a zero-row matrix, coerced to word, specifically word(matrix(integer(0),0,0))

Details

These objects are here to deal with the case where a length-zero permutation is extracted. The behaviour of these null objects is not entirely consistent.

Note

The objects documented here are distinct from the identity permutation, id, documented separately.

See Also

id

Examples

rperm(10,4)[0]  # null word

as.cycle(1:5)[0]  # null cycle

data(megaminx)
c(NULL,megaminx)      # probably not what the user intended...
c(nullcycle,megaminx) # more useful.
c(id,megaminx)        # also useful.