Rnd

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

Syntax
   Declare Function Rnd ( ByVal seed As Single = 1.0 ) As Double

Usage
   result = Rnd( seed )

Parameters
   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.

Description
   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.

   Note:
      Rnd is 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.
      Unfinished structures for other random number generators are also 
      available in the standard header "fbprng.bi".

Example
   '' 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
   Randomize

   '' 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))
      

Version
   * Before fbc 1.10.0 (for fbc 1.08.0 and fbc 1.09.0), "fbprng.bi" was 
     named "fbmath.bi".
   * Before fbc 1.08.0:
         Rnd was not thread-safe (many values temporarily returned in 
         duplicate for a same thread).
         The standard "fbmath.bi" header for available algorithms did not 
         exist.

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
   * None, if compiled in the -lang qb dialect.  Other dialects can also 
     use the same seeding and generating algorithms by calling Randomize 
     with the appropriate parameter.
   * For the non-QB-compatible algorithms, if the optional argument is 
     less than 0, it has the same meaning as passing an argument of 1.

See also
   * Randomize
   * Timer
   * Int

