Merge pull request #2690 from notoria/next

Add '$random_integer'/3

src/lib/random.pl

@@ -15,16 +15,14 @@ the random seed. This makes everything completely reproducible.
 % Succeeds with probability 0.5.
 maybe :- '$maybe'.
 
-% The higher the precision, the slower it gets.
-random_number_precision(64).
-
 %% random(-R).
 %
 % Generates a random floating number between 0 (inclusive) and 1 (exclusive).
 random(R) :-
     var(R),
-    random_number_precision(N),
-    rnd(N, R).
+    N is 2^50,
+    '$random_integer'(0, N, K),
+    R is K/N.
 
 %% random_integer(+Lower, +Upper, -R).
 %
@@ -41,25 +39,10 @@ random_integer(Lower, Upper, R) :-
         type_error(integer, Lower, random_integer/3)
     ;   \+ integer(Upper) ->
         type_error(integer, Upper, random_integer/3)
-    ;   Upper > Lower,
-        random(R0),
-        R is floor((Upper - Lower) * R0 + Lower)
+    ;   Lower < Upper,
+        '$random_integer'(Lower, Upper, R)
     ).
 
-rnd(N, R) :-
-    rnd_(N, 0, R).
-
-rnd_(0, R, R) :- !.
-rnd_(N, R0, R) :-
-    maybe,
-    !,
-    N1 is N - 1,
-    rnd_(N1, R0, R).
-rnd_(N, R0, R) :-
-    N1 is N - 1,
-    R1 is R0 + 1.0 / 2.0 ^ N,
-    rnd_(N1, R1, R).
-
 %% set_random(+Seed).
 %
 % Sets a seed that will be used for subsequent random generations in this library.