Lahey/GNU Fortran

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8.216 SELECTED_REAL_KIND — Choose real kind

Description:
SELECTED_REAL_KIND(P,R) returns the kind value of a real data type with decimal precision of at least P digits, exponent range of at least R, and with a radix of RADIX.
Standard:
Fortran 95 and later, with RADIX Fortran 2008 or later
Class:
Transformational function
Syntax:
RESULT = SELECTED_REAL_KIND([P, R, RADIX])
Arguments:

P (Optional) shall be a scalar and of type INTEGER.
R (Optional) shall be a scalar and of type INTEGER.
RADIX (Optional) shall be a scalar and of type INTEGER.
Before Fortran 2008, at least one of the arguments R or P shall be present; since Fortran 2008, they are assumed to be zero if absent.

Return value:
SELECTED_REAL_KIND returns the value of the kind type parameter of a real data type with decimal precision of at least P digits, a decimal exponent range of at least R, and with the requested RADIX. If the RADIX parameter is absent, real kinds with any radix can be returned. If more than one real data type meet the criteria, the kind of the data type with the smallest decimal precision is returned. If no real data type matches the criteria, the result is
-1 if the processor does not support a real data type with a
precision greater than or equal to P, but the R and RADIX requirements can be fulfilled
-2 if the processor does not support a real type with an exponent
range greater than or equal to R, but P and RADIX are fulfillable
-3 if RADIX but not P and R requirements
are fulfillable
-4 if RADIX and either P or R requirements
are fulfillable
-5 if there is no real type with the given RADIX

See also:
PRECISION, RANGE, RADIX
Example:
          program real_kinds
            integer,parameter :: p6 = selected_real_kind(6)
            integer,parameter :: p10r100 = selected_real_kind(10,100)
            integer,parameter :: r400 = selected_real_kind(r=400)
            real(kind=p6) :: x
            real(kind=p10r100) :: y
            real(kind=r400) :: z
          
            print *, precision(x), range(x)
            print *, precision(y), range(y)
            print *, precision(z), range(z)
          end program real_kinds