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9.211 RAND — Real pseudo-random number

Description:
RAND(FLAG) returns a pseudo-random number from a uniform distribution between 0 and 1. If FLAG is 0, the next number in the current sequence is returned; if FLAG is 1, the generator is restarted by CALL SRAND(0); if FLAG has any other value, it is used as a new seed with SRAND.

This intrinsic routine is provided for backwards compatibility with GNU Fortran 77. It implements a simple modulo generator as provided by g77. For new code, one should consider the use of RANDOM_NUMBER as it implements a superior algorithm.

Standard:
GNU extension
Class:
Function
Syntax:
RESULT = RAND(I)
Arguments:

I Shall be a scalar INTEGER of kind 4.

Return value:
The return value is of REAL type and the default kind.
Example:
          program test_rand
            integer,parameter :: seed = 86456
          
            call srand(seed)
            print *, rand(), rand(), rand(), rand()
            print *, rand(seed), rand(), rand(), rand()
          end program test_rand

See also:
SRAND, RANDOM_NUMBER