!########################################################################!

 MODULE const_and_precisions
!########################################################################!
 IMPLICIT NONE
 PUBLIC
!------------------------------------------------------------------------
! common precisions
!------------------------------------------------------------------------
!  INTEGER, PARAMETER :: i1 = SELECTED_INT_KIND (2)        ! Integer*1
!  INTEGER, PARAMETER :: i2 = SELECTED_INT_KIND (4)        ! Integer*2
  INTEGER, PARAMETER :: i4 = SELECTED_INT_KIND (9)        ! Integer*4
  INTEGER, PARAMETER :: i8 = SELECTED_INT_KIND (18)       ! Integer*8
  INTEGER, PARAMETER :: r4 = SELECTED_REAL_KIND (6, 37)   ! Real*4
  INTEGER, PARAMETER :: r8 = SELECTED_REAL_KIND (15, 300) ! Real*8
! INTEGER, PARAMETER :: sp_   = r4        ! single precision
! INTEGER, PARAMETER :: dp_   = r8        ! double precision
  INTEGER, PARAMETER :: wp_   = r8        ! work-precision
! INTEGER, PARAMETER :: odep_ = dp_       ! ODE-solver precision
! INTEGER, PARAMETER :: xp_   = wp_       ! for ext. modules if necessary
!------------------------------------------------------------------------
! precisions which are in use in CONFIG_yat
!------------------------------------------------------------------------
! INTEGER, PARAMETER :: ypi_ = 4          ! <- direct precision def.
! INTEGER, PARAMETER :: ypd_ = 8          ! <- direct precision def.
!------------------------------------------------------------------------
! length of the file names
!------------------------------------------------------------------------
 !INTEGER, PARAMETER :: lfn_ = 256        ! <- requested for yat
!!========================================================================
! Arithmetic constants
!========================================================================
  integer,   parameter :: izero   = 0
  REAL(wp_), PARAMETER :: zero    = 0.0_wp_
  REAL(wp_), PARAMETER :: half    = 0.5_wp_
  REAL(wp_), PARAMETER :: one     = 1.0_wp_
  REAL(wp_), PARAMETER :: two     = 2.0_wp_
  real(wp_), parameter :: pi      = 3.141592653589793_wp_  ! 3.141592653589793238462643383280
  real(wp_), parameter :: pihalf  = 1.57079632679489661923_wp_
  REAL(wp_), PARAMETER :: sqrt_pi = 1.772453850905516_wp_
! REAL(wp_), PARAMETER :: sqrt_2  = 1.414213562373095_wp_
  REAL(wp_), PARAMETER :: degree  = pi/180.0_wp_
  REAL(wp_), PARAMETER :: emn1    = 0.367879441171442_wp_  ! exp(-1)
!---
! REAL(wp_), PARAMETER :: ex(1:3) = (/one ,zero,zero/)
! REAL(wp_), PARAMETER :: ey(1:3) = (/zero,one ,zero/)
! REAL(wp_), PARAMETER :: ez(1:3) = (/zero,zero,one /)
!---
! REAL(wp_), PARAMETER :: kron(3,3) = reshape((/one ,zero,zero, &
!                                               zero,one ,zero, &
!                                               zero,zero,one /),(/3,3/))
  COMPLEX(wp_), PARAMETER :: im    = (0.0_wp_,1.0_wp_)
  COMPLEX(wp_), PARAMETER :: czero = (0.0_wp_,0.0_wp_)
  COMPLEX(wp_), PARAMETER :: cunit = (1.0_wp_,0.0_wp_)
! COMPLEX(wp_), PARAMETER :: ctwo  = (2.0_wp_,0.0_wp_)
!========================================================================
! Computer constants
!========================================================================
  REAL(wp_), PARAMETER :: comp_eps      = EPSILON(one)
! REAL(wp_), PARAMETER :: comp_eps2     = comp_eps**2
  REAL(wp_), PARAMETER :: comp_tiny     = TINY(one)
  REAL(wp_), PARAMETER :: comp_huge     = HUGE(one)
! REAL(wp_), PARAMETER :: comp_tinylog  =-200 ! LOG10(comp_tiny)
! REAL(wp_), PARAMETER :: comp_hugelog  =+200 ! LOG10(comp_huge)
! REAL(wp_), PARAMETER :: comp_tiny1    = 1d+50*comp_tiny
! REAL(wp_), PARAMETER :: comp_huge1    = 1d-50*comp_huge
! REAL(wp_), PARAMETER :: comp_tiny1log = LOG10(comp_tiny1)
! REAL(wp_), PARAMETER :: comp_huge1log = LOG10(comp_huge1)
!------------------------------------------------------------------------
! Conventional constants
!------------------------------------------------------------------------
  INTEGER,  PARAMETER :: int_invalid = -999999999
  REAL(R8), PARAMETER :: r8_invalid = -9.0e40_r8
! REAL(wp_), PARAMETER :: output_tiny = 1.0d-66
! REAL(wp_), PARAMETER :: output_huge = 1.0d+66
!========================================================================
! Physical constants (SI)
!========================================================================
  real (wp_), parameter :: e_ = 1.602176487e-19_wp_         ! elementary charge, C
  real (wp_), parameter :: me_ = 9.10938215e-31_wp_         ! electron mass, kg
! real (wp_), parameter :: mp_ = 1.672621637e-27_wp_        ! proton mass, kg
! real (wp_), parameter :: md_ = 3.34358320e-27_wp_         ! deuteron mass, kg
! real (wp_), parameter :: mt_ = 5.00735588e-27_wp_         ! triton mass, kg
! real (wp_), parameter :: ma_ = 6.64465620e-27_wp_         ! alpha mass, kg
! real (wp_), parameter :: amu_ = 1.660538782e-27_wp_       ! amu, kg
! REAL (wp_), PARAMETER :: rmpe_  = mp_/me_                 ! proton-electron mass ratio
  real (wp_), parameter :: c_ = 2.99792458e8_wp_            ! speed of light, m/s
  real (wp_), parameter :: mu0_ = 4.0e-7_wp_ * pi           ! magnetic permeability of vacuum
  real (wp_), parameter :: eps0_ = 1.0_wp_ / (mu0_ * c_**2) ! dielectric constant of vacuum, F/m
! real (wp_), parameter :: avogr = 6.02214179e23_wp_
! real (wp_), parameter :: KBolt = 1.3806504e-23_wp_
!========================================================================
! Physical constants (cgs)
!========================================================================
  real (wp_), parameter :: ccgs_ = c_*1.e2_wp_              ! speed of light, cm/s
  real (wp_), parameter :: mecgs_ = me_*1.e3_wp_            ! electron mass, g
  real (wp_), parameter :: ecgs_ = e_*c_*10._wp_            ! elementary charge, statcoul
!------------------------------------------------------------------------
! Useful definitions
!------------------------------------------------------------------------
  REAL(wp_), PARAMETER :: keV_   = 1.e3_wp_*e_     ! [J]
  REAL(wp_), PARAMETER :: mc2_SI = me_*c_**2       ! [J]
  REAL(wp_), PARAMETER :: mc2_   = mc2_SI/keV_     ! [keV]
  REAL(wp_), PARAMETER :: mu0inv = 1._wp_/mu0_     !
! REAL(wp_), PARAMETER :: mc_    = me_*c_          ! [kg*m/s]
! ! f_ce = fce1_*B (B in Tesla):                   !
  REAL(wp_), PARAMETER :: wce1_  = e_/me_          ! [rad/s]
! REAL(wp_), PARAMETER :: fce1_  = wce1_/(2*pi)    ! [1/s]
! ! f_pl = fpe1_*sqrt(Ne) (Ne in 1/m**3):          !
! REAL(wp_), PARAMETER :: wpe1_  = 56.4049201      ! [rad/s]
! REAL(wp_), PARAMETER :: fpe1_  = wpe1_/(2*pi)    ! [1/s]
! REAL(wp_), PARAMETER :: wpe12_ = wpe1_**2        !
! ! vte  = vte1_*sqrt(Te) (Te in keV):             !
! REAL(wp_), PARAMETER :: vte1_  = 1.8755328e7     ! [m/s]
! ! je   = curr1_*sqrt(Te)*Ne  (Ne in 1/m**3):     !
! REAL(wp_), PARAMETER :: curr1_ = e_*vte1_        ! [A/m**2]
!!========================================================================
!! Upper limit for the momentum value for integration
!!========================================================================
! REAL(wp_), PARAMETER :: umax_ = 7.0d0            ! max of (p/pth)
! INTEGER,   PARAMETER :: nu_   = 700              ! size of upar-array
!========================================================================
! minimal value of Nparallel
!========================================================================
! REAL(wp_), PARAMETER :: Npar_min = 1.0d-3
!########################################################################!

  interface is_valid
     module procedure is_valid_int4, is_valid_int8, is_valid_real8
  end interface

contains

  logical function is_valid_int4(in_int)
    implicit none
    integer(i4), intent(in) :: in_int
    is_valid_int4 = in_int /= int_invalid
    return
  end function is_valid_int4

  logical function is_valid_int8(in_int)
    implicit none
    integer(i8), intent(in) :: in_int
    is_valid_int8 = in_int /= int_invalid
    return
  end function is_valid_int8

  logical function is_valid_real8(in_real)
    implicit none
    real(r8), intent(in) :: in_real
    is_valid_real8 = abs(in_real - r8_invalid) > abs(r8_invalid) * 1.0e-15_r8
    return
  end function is_valid_real8

 END MODULE const_and_precisions

!########################################################################!