Local recursion with access to lexical scope.

iter.erl

-module(iter).
-export([fac/1]).
-define( for(Arg,Seed,Body)
       , begin F = fun(Iter,Arg)->Body end, F(F,Seed) end
       ).
-define( iter(Arg)
       , Iter(Iter,Arg)
       ).


fac(N)->
    ?for({I,Y}, {N,1},
        case (I>1) of
            true -> ?iter({I-1,Y*I});
            false -> Y
        end).