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I need to generate a random integer between 1 and n (where n is a positive whole number) to use for a unit test. I don't need something overly complicated to ensure true randomness - just an old-fashioned random number.
How would I do that?
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Random numbers can be generated by the Visual Basic Rnd() function, that returns a floating-point value between 0.0 and 1.0. Multiplying the random numbers will specify a wider range. For example, a multiplier of 20 will create a random number between zero and 20.
Rnd() Returns a random number of type Single. Rnd(Single) Returns a random number of type Single.
The rand function in C In C rand() returns a value between 0 and a large integer (called by the name "RAND_MAX" found in stdlib. h).
As has been pointed out many times, the suggestion to write code like this is problematic:
Public Function GetRandom(ByVal Min As Integer, ByVal Max As Integer) As Integer Dim Generator As System.Random = New System.Random() Return Generator.Next(Min, Max) End Function The reason is that the constructor for the Random class provides a default seed based on the system's clock. On most systems, this has limited granularity -- somewhere in the vicinity of 20 ms. So if you write the following code, you're going to get the same number a bunch of times in a row:
Dim randoms(1000) As Integer For i As Integer = 0 to randoms.Length - 1 randoms(i) = GetRandom(1, 100) Next The following code addresses this issue:
Public Function GetRandom(ByVal Min As Integer, ByVal Max As Integer) As Integer ' by making Generator static, we preserve the same instance ' ' (i.e., do not create new instances with the same seed over and over) ' ' between calls ' Static Generator As System.Random = New System.Random() Return Generator.Next(Min, Max) End Function I threw together a simple program using both methods to generate 25 random integers between 1 and 100. Here's the output:
Non-static: 70 Static: 70 Non-static: 70 Static: 46 Non-static: 70 Static: 58 Non-static: 70 Static: 19 Non-static: 70 Static: 79 Non-static: 70 Static: 24 Non-static: 70 Static: 14 Non-static: 70 Static: 46 Non-static: 70 Static: 82 Non-static: 70 Static: 31 Non-static: 70 Static: 25 Non-static: 70 Static: 8 Non-static: 70 Static: 76 Non-static: 70 Static: 74 Non-static: 70 Static: 84 Non-static: 70 Static: 39 Non-static: 70 Static: 30 Non-static: 70 Static: 55 Non-static: 70 Static: 49 Non-static: 70 Static: 21 Non-static: 70 Static: 99 Non-static: 70 Static: 15 Non-static: 70 Static: 83 Non-static: 70 Static: 26 Non-static: 70 Static: 16 Non-static: 70 Static: 75 To get a random integer value between 1 and N (inclusive) you can use the following.
CInt(Math.Ceiling(Rnd() * n)) + 1 If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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