Writing a Factorial function with Lists

Question

While I believe I have found a sound algorithm for my function (Factorial) I'm very confused as to why it loops infinitely. Here's my code :

declare
fun{Fact N}
   local M=1 in             %I suppose it loops from here??
      local FactT in        %But the function call starts from here
     fun{FactT N Acc}       % which doesn't include the local declaration of M
        if M==N then
           {Browse M}
           Acc
        else
           %{Browse M}     %displays infinite lines of 1s
           %{Browse N}
           %{Browse Acc}   %They form a continuously growing list of 1s
           {FactT (M+1) (M|Acc)}end
     end
     {FactT N nil}
      end
   end
end

{Browse {Fact 3}}

Answer 1

You never increment M => {Fact (M+1) (M|Acc}} is always {Fact 2 1|Acc}

and to make your code more readable, you're not obilged to write

fun...
   local ...
   in ...
   end
end

you can just write

fun...
   ...
in
   ...
end

---

code

Taking those things into account, the most simple factorial function is

declare
fun {Fact N}
   fun{Aux N Acc}
      if N=<0 then Acc
      else {Aux N-1 N*Acc}
      end
   end
in
   {Aux N 1}
end