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Improve ernd as &rnd( 2) always returned same pattern.

This commit is contained in:
Renaud 2017-05-14 15:18:28 +08:00
parent ba87641122
commit 918a310601
1 changed files with 9 additions and 9 deletions
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18
eval.c
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@ -1320,19 +1320,19 @@ char *mklower(char *str)
/*
* returns a random integer
* ernd( 0) [ 0 .. 2147483647]
* ernd( i) [ 1 .. abs( i)]
* ernd( 1) [ 1]
* ernd( -2147483648) [ 1 .. 2147483647] actually 2147482413
* ernd( 0) [ 0 .. 2147483647]
* ernd( -2147483648) [ 0 .. 2147483647]
* ernd( 1) [ 1]
* ernd( i) [ 1 .. abs( i)]
*/
static int ernd( int i) {
seed = seed * 1721 + 10007 ;
seed &= ~(1 << 31) ; /* avoid abs() which introduces 176719 periodicity */
if( i == 0)
return seed ;
int s ;
seed = seed * 1721 + 10007 ;
s = ((seed >> 16) & 0x0000FFFF) | (seed << 16) ;
s &= ~(1 << 31) ; /* avoid abs() */
i = i < 0 ? -i : i ; /* abs( i) */
return seed % i + 1 ;
return (i <= 0) ? s : s % i + 1 ;
}
/*