1 files changed, 34 insertions, 13 deletions

diff --git a/src/func.cc b/src/func.cc
index e427bf2..5dcb3e9 100644
--- a/src/func.cc
+++ b/src/func.cc
@@ -35,6 +35,28 @@
 #include "stl-utils.h"
 #include "printutils.h"
 
+/*
+ Random numbers
+
+ Newer versions of boost/C++ include a non-deterministic random_device and
+ auto/bind()s for random function objects, but we are supporting older systems.
+*/
+
+#include <boost/random/mersenne_twister.hpp>
+#include <boost/random/uniform_real_distribution.hpp>
+
+#ifdef __WIN32__
+#include <process.h>
+int process_id = _getpid();
+#else
+#include <sys/types.h>
+#include <unistd.h>
+int process_id = getpid();
+#endif
+
+boost::random::mt19937 deterministic_rng;
+boost::random::mt19937 lessdeterministic_rng( std::time(0) + process_id );
+
 AbstractFunction::~AbstractFunction()
 {
 }
@@ -119,24 +141,15 @@ Value builtin_sign(const Context *, const std::vector<std::string>&, const std::
 	return Value();
 }
 
-double frand() 
-{ 
-    return rand()/(double(RAND_MAX)+1); 
-} 
-
-double frand(double min, double max) 
-{ 
-    return (min>max) ? frand()*(min-max)+max : frand()*(max-min)+min;  
-} 
-
 Value builtin_rands(const Context *, const std::vector<std::string>&, const std::vector<Value> &args)
 {
+	bool deterministic = false;
 	if (args.size() == 3 &&
 			args[0].type() == Value::NUMBER && 
 			args[1].type() == Value::NUMBER && 
 			args[2].type() == Value::NUMBER)
 	{
-		srand((unsigned int)time(0));
+		deterministic = false;
 	}
 	else if (args.size() == 4 && 
 					 args[0].type() == Value::NUMBER && 
@@ -144,16 +157,24 @@ Value builtin_rands(const Context *, const std::vector<std::string>&, const std:
 					 args[2].type() == Value::NUMBER && 
 					 args[3].type() == Value::NUMBER)
 	{
-		srand((unsigned int)args[3].toDouble());
+		deterministic_rng.seed( (unsigned int) args[3].toDouble() );
+		deterministic = true;
 	}
 	else
 	{
 		return Value();
 	}
 	
+	double min = std::min( args[0].toDouble(), args[1].toDouble() );
+	double max = std::max( args[0].toDouble(), args[1].toDouble() );
+	boost::random::uniform_real_distribution<> distributor( min, max );
 	Value::VectorType vec;
 	for (int i=0; i<args[2].toDouble(); i++) {
-		vec.push_back(Value(frand(args[0].toDouble(), args[1].toDouble())));
+		if ( deterministic ) {
+			vec.push_back( Value( distributor( deterministic_rng ) ) );
+		} else {
+			vec.push_back( Value( distributor( lessdeterministic_rng ) ) );
+		}
 	}
 	
 	return Value(vec);