Rand

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Definition

INT rand ( <INT lowerlimit> , <INT upperlimit> )

Returns a random number, ranging from a certain lower limit to a certain upper limit. The limits are within the range.

Make sure the difference between lowerlimit and upperlimit does not exceed 32767 (2^15-1). If that is needed, the function rand2() below can be used.

Parameters

INT lowerlimit - The lower limit for the random value.
INT upperlimit - The upper limit for the random value.

Returns

INT : A random value: lowerlimit <= result <= upperlimit

Notes

To synchronize rand() on different computers, the function rand_seed() can be used.

Rand() is not a very good function on itself. To counter this, the following rand2() can be used:

#define RAND_MAX 32767
#define DRAND_RANGE (1.0/((RAND_MAX + 1)*(RAND_MAX + 1)))
#define irand(x) ((unsigned int) ((x) * drand ()))
Function float drand ()
Private
    float f;
Begin
    Repeat
       f = (rand (0,RAND_MAX) * (RAND_MAX + 1.0)
          + rand (0,RAND_MAX)) * DRAND_RANGE;
    Until (f < 1); /* Round off */
    return f;
End
Function int rand2(int lowerlimit, int upperlimit)
Begin
    return (lowerlimit+irand(upperlimit-lowerlimit+1));
End

To understand this code, one can read its source.


Mod_rand
Functions Rand()Randseed()