[rwm] -- I thought the [primes] page was getting too crowded so I added this as a new page.  My intent on adding this
was to help teach the math and provide a simple Tcl implementation of the algorithm.  (It might belong in a cookbook of
useful recipes??)

'''Warning''' - Note that It only checks 'a'=2 which will include some 'liars'.
It could be changed to check other a values as well.

References:

   1.  http://en.wikipedia.org/wiki/Fermat_primality_test

Dependencies:

   1. binaryModExpo - a modular exponentiation function (I like the one at the bottom of [RSA in Tcl])

======
proc primeCheckFermat {p} {
  ## based on fermats little theorem
  ## a**(p-1) == 1
  ## for a in the interval [1,p-1]

  if {[binaryModExpo 2 $p $p] == 2} {
    # possible prime (or fermat liar)
    return 1
  } else {
    #puts stderr "failed fermat check ..."
    # not possible
    return 0
  }
}
======

<<categories>> Mathematics | Arts and crafts of Tcl-Tk programming