The GNU Fortran Compiler: SELECTED_REAL_KIND

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### 8.217 `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

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