49.7.1 Miscellaneous utility functions

The following bindings are exported by the (vicare crypto randomisations) library.

Function: random-source-integers-maker-from-range source start last

Function: random-source-integers-maker-from-range source start last step

Return a closure that, when evaluated with no arguments, returns a random integer in the range selected by start and last both included, using randomness from source. start and last must be exact integers. The optional step argument, which defaults to one, establishes the step of allowed values from the range.

Function: random-source-reals-maker-from-range source start last

Function: random-source-reals-maker-from-range source start last step

Return a closure that, when evaluated with no arguments, returns a random real in the range selected by start and last, using randomness from source. start and last must be real numbers.

• When step is not used: The result R is computed by generating a random real X in the range 0 < X < 1, then computing:

  R = start + (last - start) * X
  

  so R is in the range delimited by start and last both excluded. The random real X is computed with no specified unit. random-source-reals-maker, for details.

• When step is used: The result R is computed by generating a random integer N in the range 0 <= N < U with upper limit:

  U = floor[(last - start) / step]
  

  then computing:

  R = start + step * N
  

  so R is in the range delimited by start included and last excluded.

Function: random-permutations-maker source

Return a closure which, when applied to an integer number n, generates random permutations of the set {0, ..., n-1} using randomness from source. Such a permutation is represented by a vector of length n for the images of the points.