as.function.permutation: Coerce a permutation to a function

In permutations: The Symmetric Group: Permutations of a Finite Set

Coerce a permutation to a function

Description

Coerce a permutation to an executable function

Usage

## S3 method for class 'permutation'
as.function(x, ...)

Arguments

x	permutation
...	further arguments (currently ignored)

Note

Multiplication of permutations loses associativity when using functional notation; see examples.

Also, note that the coerced function will not take an argument greater than the size (qv) of the permutation.

Author(s)

Robin K. S. Hankin

Examples

x <- cyc_len(3)
y <- cyc_len(5)

xfun <- as.function(x)
yfun <- as.function(y)

stopifnot(xfun(yfun(2)) == as.function(y*x)(2)) # note transposition of x & y

# written in postfix notation one has the very appealing form x(fg) = (xf)g

# it's vectorized:
as.function(rperm(10,9))(1)   
as.function(as.cycle(1:9))(sample(9))

permutations documentation built on Sept. 11, 2024, 6:10 p.m.