Returns a random double precision number in the range [0, 1)

declare function Rnd ( byval seed as single = 1.0 ) as double

result = Rnd( seed )

Optional single argument. If seed has a value of zero (0.0), the last random number generated is repeate. For any other number a new random number is returned. With the QB-compatible algorithm, a negative number fully reseeds the generator. The default for no argument is to return a new random number.

Return Value:
Returns the random number generated.

Returns a number of type double in the range [0, 1) (i.e. 0 <= Rnd < 1), based on a random seed (see Randomize).

Rnd can use a variety of different algorithms - see Randomize for details of the default and selectable algorithms.

Rnd will return the same sequence of numbers every time a program is run. This sequence can be changed by reseeding the generator.

- For fbc version < 1.08, Rnd is not thread-safe. Used in the context of a multi-threaded program with race conditions due to asynchronous calls to Rnd, many values ​​are temporarily returned in duplicate for a same thread.
- For fbc version >= 1.08, Rnd is became thread-safe (by using an internal mutex), but not thread specific. Used in the context of a multi-threaded program, only the execution speed is significantly slowed down compared to a single thread call context. Structures for other random number generators are also now available in the standard header "fbmath.bi".

'' Function to a random number in the range [first, last), or {first <= x < last}.
Function rnd_range (first As Double, last As Double) As Double
    Function = Rnd * (last - first) + first
End Function

'' seed the random number generator, so the sequence is not the same each time

'' prints a random number in the range [0, 1), or {0 <= x < 1}.
Print Rnd

'' prints a random number in the range [0, 10), or  {0 <= x < 10}.
Print Rnd * 10

'' prints a random integral number in the range  [1, 10], or {1 <= n <= 10}.
''     (because: 0 <= Rnd * 10 < 10)
Print Int(Rnd * 10) + 1

'' prints a random integral number in the range [69, 420], or {69 <= n <= 420}.
''     (because: 69 <= rnd_range(69, 421) < 421)
Print Int(rnd_range(69, 421))

Dialect Differences:
The default algorithm used depends on the current dialect in use:
  • With the -lang fb dialect, a 32 bit Mersenne Twister function with a granularity of 32 bits is used.
  • With the -lang qb dialect, a function giving the same output as Rnd in QB is used. The granularity is 24 bits.
  • With the -lang deprecated and -lang fblite dialects, the function in the C runtime available in the system is used. The function available in Win32 has a granularity of 15 bits, and 32 bits in Linux and DOS.

Differences from QB:
See also:
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