[mercury-users] Converting time_t to int using common library?

[Julian Fondren]

On 2/13/07, doug.auclair at logicaltypes.com <doug.auclair at logicaltypes.com> wrote:
> So, is there an elegant way to convert time_t to int
> using the supplied modules in the library that I'm
> missing?  If not, could module random be modified
> to allow a seed to initialize the supply to be a time_t
> as well as an int?

As an alternate solution, attached is a a patch that
adds to library/random.m ; see docs, below.

Cheers,
Julian


        % random.init(RS, !IO): creates a supply of random numbers RS
        % using a sensible default seed (e.g., on POSIX it will use
        % the number of seconds since the unix epoch.)
        %
:- pred random.init(random.supply::uo, io::di, io::uo) is det.

        % random.init(RS): creates a supply of random numbers RS
        % using a sensible default seed (e.g., on POSIX it will use
        % the number of seconds since the unix epoch.)  This function
        % differs from the previous predicate in that it only determines
        % the 'sensible default seed' when first evaluated, and
        % thereafter uses that same seed.
        %
:- func random.init = (random.supply::uo) is det.
-------------- next part --------------
*** mercury-compiler-0.13.1/library/random.m	Mon Jul 31 15:01:56 2006
--- random.m	Tue Feb 13 05:31:37 2007
***************
*** 53,59 ****
  
  :- import_module list.
  
  	% The type `random.supply' represents a supply of random numbers.
!     %
  :- type random.supply.
  
--- 53,60 ----
  
  :- import_module list.
+ :- import_module io.
  
  	% The type `random.supply' represents a supply of random numbers.
! 	%
  :- type random.supply.
  
***************
*** 63,69 ****
--- 64,86 ----
  :- pred random.init(int::in, random.supply::uo) is det.
  
+ 	% random.init(RS, !IO): creates a supply of random numbers RS
+ 	% using a sensible default seed (e.g., on POSIX it will use
+ 	% the number of seconds since the unix epoch.)
+ 	%
+ :- pred random.init(random.supply::uo, io::di, io::uo) is det.
+ 
+ 	% random.init(RS): creates a supply of random numbers RS
+ 	% using a sensible default seed (e.g., on POSIX it will use
+ 	% the number of seconds since the unix epoch.)  This function
+ 	% differs from the previous predicate in that it only determines
+ 	% the 'sensible default seed' when first evaluated, and
+ 	% thereafter uses that same seed.
+ 	%
+ :- func random.init = (random.supply::uo) is det.
+ 
  	% random.random(Num, RS0, RS): extracts a number Num in the
  	% range 0 .. RandMax from the random number supply RS0, and
  	% binds RS to the new state of the random number supply.
+ 	%
  :- pred random.random(int, random.supply, random.supply).
  :- mode random.random(out, mdi, muo) is det.
***************
*** 134,137 ****
--- 151,177 ----
  random.init(I0, rs(RS)) :-
  	copy(I0, RS).
+ 
+ :- pragma promise_pure(random.init/3).
+ random.init(rs(RS), !IO) :-
+ 	semipure random.generate_seed(Seed),
+     copy(Seed, RS).
+ 
+ :- pragma promise_pure(random.init/0).
+ :- mutable(generated_seed, int, 0, ground, [untrailed]).
+ random.init = rs(RS) :-
+ 	semipure random.get_generated_seed(Seed),
+ 	( Seed = 0 ->
+ 		semipure random.generate_seed(NewSeed),
+ 		impure random.set_generated_seed(NewSeed),
+         copy(NewSeed, RS)
+ 	;
+         copy(Seed, RS)
+ 	).
+ 
+ :- pragma c_header_code("#include <time.h>").
+ :- semipure pred random.generate_seed(int::out) is det.
+ :- pragma c_code(random.generate_seed(Time::out),
+ 		[will_not_call_mercury, thread_safe, promise_semipure],
+ 		"Time = time(NULL);").
  
  random.random(I, rs(RS0), rs(RS)) :-