1 files changed, 99 insertions, 0 deletions
diff --git a/labb5/lib/StanfordCPPLib/random.cpp b/labb5/lib/StanfordCPPLib/random.cpp
new file mode 100755
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+++ b/labb5/lib/StanfordCPPLib/random.cpp
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+/*
+ * File: random.cpp
+ * ----------------
+ * This file implements the random.h interface.
+ */
+
+#include <cstdlib>
+#include <cmath>
+#include <ctime>
+#include "random.h"
+#include "private/randompatch.h"
+using namespace std;
+
+/* Private function prototype */
+
+static void initRandomSeed();
+
+/*
+ * Implementation notes: randomInteger
+ * -----------------------------------
+ * The code for randomInteger produces the number in four steps:
+ *
+ * 1. Generate a random real number d in the range [0 .. 1).
+ * 2. Scale the number to the range [0 .. N) where N is the number of values.
+ * 3. Translate the number so that the range starts at the appropriate value.
+ * 4. Convert the result to the next lower integer.
+ *
+ * The implementation is complicated by the fact that both the expression
+ *
+ *     RAND_MAX + 1
+ *
+ * and the expression for the number of values
+ *
+ *     high - low + 1
+ *
+ * can overflow the integer range.  These calculations must therefore be
+ * performed using doubles instead of ints.
+ */
+
+int randomInteger(int low, int high) {
+   initRandomSeed();
+   double d = rand() / (double(RAND_MAX) + 1);
+   double s = d * (double(high) - low + 1);
+   return int(floor(low + s));
+}
+
+/*
+ * Implementation notes: randomReal
+ * --------------------------------
+ * The code for randomReal is similar to that for randomInteger,
+ * without the final conversion step.
+ */
+
+double randomReal(double low, double high) {
+   initRandomSeed();
+   double d = rand() / (double(RAND_MAX) + 1);
+   double s = d * (high - low);
+   return low + s;
+}
+
+/*
+ * Implementation notes: randomChance
+ * ----------------------------------
+ * The code for randomChance calls randomReal(0, 1) and then checks
+ * whether the result is less than the requested probability.
+ */
+
+bool randomChance(double p) {
+   initRandomSeed();
+   return randomReal(0, 1) < p;
+}
+
+/*
+ * Implementation notes: setRandomSeed
+ * -----------------------------------
+ * The setRandomSeed function simply forwards its argument to srand.
+ * The call to initRandomSeed is required to set the initialized flag.
+ */
+
+void setRandomSeed(int seed) {
+   initRandomSeed();
+   srand(seed);
+}
+
+/*
+ * Implementation notes: initRandomSeed
+ * ------------------------------------
+ * The initRandomSeed function declares a static variable that keeps track
+ * of whether the seed has been initialized.  The first time initRandomSeed
+ * is called, initialized is false, so the seed is set to the current time.
+ */
+
+static void initRandomSeed() {
+   static bool initialized = false;
+   if (!initialized) {
+      srand(int(time(NULL)));
+      initialized = true;
+   }
+}