src/core/random_func.hpp
branchnoai
changeset 9723 eee46cb39750
parent 9722 ebf0ece7d8f6
child 9724 b39bc69bb2f2
--- a/src/core/random_func.hpp	Fri Nov 23 16:59:30 2007 +0000
+++ b/src/core/random_func.hpp	Wed Jan 09 18:11:12 2008 +0000
@@ -5,6 +5,11 @@
 #ifndef RANDOM_FUNC_HPP
 #define RANDOM_FUNC_HPP
 
+#if defined(__APPLE__)
+	/* Apple already has Random declared */
+	#define Random OTTD_Random
+#endif /* __APPLE__ */
+
 /**************
  * Warning: DO NOT enable this unless you understand what it does
  *
@@ -36,4 +41,65 @@
 uint32 InteractiveRandom(); // Used for random sequences that are not the same on the other end of the multiplayer link
 uint InteractiveRandomRange(uint max);
 
+/**
+ * Checks if a given randomize-number is below a given probability.
+ *
+ * This function is used to check if the given probability by the fraction of (a/b)
+ * is greater than low 16 bits of the given randomize-number v.
+ *
+ * Do not use this function twice on the same random 16 bits as it will yield
+ * the same result. One can use a random number for two calls to Chance16I,
+ * where one call sends the low 16 bits and the other the high 16 bits.
+ *
+ * @param a The numerator of the fraction
+ * @param b The denominator of the fraction, must of course not be null
+ * @param r The given randomize-number
+ * @return True if v is less or equals (a/b)
+ */
+static inline bool Chance16I(const uint a, const uint b, const uint32 r)
+{
+	assert(b != 0);
+	return (uint16)r < (uint16)((a << 16) / b);
+}
+
+/**
+ * Flips a coin with a given probability.
+ *
+ * This macro can be used to get true or false randomized according to a
+ * given probability. The parameter a and b create a percent value with
+ * (a/b). The macro returns true in (a/b) percent.
+ *
+ * @see Chance16I()
+ * @param a The numerator of the fraction
+ * @param b The denominator of the fraction
+ * @return True in (a/b) percent
+ */
+static inline bool Chance16(const uint a, const uint b)
+{
+	return Chance16I(a, b, Random());
+}
+
+/**
+ * Flips a coin with a given probability and saves the randomize-number in a variable.
+ *
+ * This function uses the same parameters as Chance16. The third parameter
+ * must be a variable the randomize-number from Random() is saved in.
+ *
+ * The low 16 bits of r will already be used and can therefor not be passed to
+ * Chance16I. One can only send the high 16 bits to Chance16I.
+ *
+ * @see Chance16I()
+ * @param a The numerator of the fraction
+ * @param b The denominator of the fraction
+ * @param r The variable to save the randomize-number from Random()
+ * @return True in (a/b) percent
+ */
+static inline bool Chance16R(const uint a, const uint b, uint32 &r)
+{
+	r = Random();
+	return Chance16I(a, b, r);
+}
+
+extern uint32 _random_seeds[2][2];
+
 #endif /* RANDOM_FUNC_HPP */