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digitalmars.D.learn - random number within a specified range?

reply Michael P. <baseball.mjp gmail.com> writes:
Hi,

How would I go about getting a random number that was in a specified range of 2
numbers?
For example, getting a number inbetween 1000 and 2000.

-Michael P.
Oct 05 2008
parent reply "Jarrett Billingsley" <jarrett.billingsley gmail.com> writes:
On Sun, Oct 5, 2008 at 7:34 PM, Michael P. <baseball.mjp gmail.com> wrote:
 Hi,

 How would I go about getting a random number that was in a specified range of
2 numbers?
 For example, getting a number inbetween 1000 and 2000.

 -Michael P.

lo + rand() % (hi - lo) assuming you're using Phobos, where rand() returns a number in the range [0, uint.max]. This will get you a number in the range [1000, 2000); that is, it will be at least 1000 and at most 1999. If you need 2000 to be one of the numbers generated, use 2001 as the hi.
Oct 05 2008
parent Don <nospam nospam.com.au> writes:
Jarrett Billingsley wrote:
 On Sun, Oct 5, 2008 at 7:34 PM, Michael P. <baseball.mjp gmail.com> wrote:
 Hi,

 How would I go about getting a random number that was in a specified range of
2 numbers?
 For example, getting a number inbetween 1000 and 2000.

 -Michael P.

lo + rand() % (hi - lo) assuming you're using Phobos, where rand() returns a number in the range [0, uint.max]. This will get you a number in the range [1000, 2000); that is, it will be at least 1000 and at most 1999. If you need 2000 to be one of the numbers generated, use 2001 as the hi.

more which are closer to 1000 than to 2000. (Imagine uint.max = 1000. Then 0 and 1000 map to 1000, but every other number has only one number which maps to it). Simple way to fix this is to ignore numbers from the non-uniform part: uint rmax = uint.max - (uint.max % (hi-lo)); uint r; do { r = rand(); } while (r>rmax); return lo + r % (hi - lo);
Oct 09 2008