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CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v102a/clib/rand.lis

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+1File: rand.c                                                              Page       1
+     1   /* rand.c - kluges a random number generator with addition & overflow */
+     2   #include <portab.h>
+     3    
+     4    
+     5   #define NSEEDS 7
+     6    
+     7   MLOCAL UWORD _seeds[NSEEDS] =
+     8   	{ 0, 24213, 12345, 4622, 2143, 32010, 7942 };
+     9    
+    10   MLOCAL WORD _seedptr=0;
+    11    
+    12    
+    13   WORD srand(seed1)
+    14   	int seed1;
+    15   {
+    16   	WORD ncs;
+    17   	_seeds[0] = seed1;
+    18   	for( ncs = seed1&077; ncs; ncs-- )
+    19   		rand();
+    20   	return(rand());
+    21   }
+    22    
+    23    
+    24   WORD rand()
+    25   {
+    26   	UWORD tot, ii;
+    27    
+    28   	for( tot=0, ii=0; ii<NSEEDS; ii++)
+    29   		tot += _seeds[ii];	/* ignore overflow */
+    30   	if( ++_seedptr >= NSEEDS )
+    31   		_seedptr = 0;
+    32   	_seeds[_seedptr] = tot;
+    33   	return( tot >> 1 );		/* ignore lo bit because of addition */
+    34   }
+    35