program Aug02_2002
   implicit none
   integer::range,i,j,k,gcd,ell,blank_count
! Notice that the type of plus_plus does not have to be specified
   real::round,v,m
   character::letter_grade
   character(40)::myword
   print*,sqrt(2.0),round(sqrt(2.0),3)
   do i = 50,99,7
    print*,"A numeric score of ",i," yields a letter grade of ",letter_grade(i)
   end do
   ell = 18
   j = 5
   if(plus_plus(j) == 6) print*,'plus_plus(j) == 6'
   print*,'j = ',j
   if(plus_plus(5) == 6) print*,'plus_plus(5) == 6'  ! Illegal Statement
   print*,'5 = ',5
   myword = "I think therefore I am"
   print*,"The word 'myword' has",blank_count(myword),"blanks"
   print*,"and should be written as '",trim(myword),"'"
   call get_volume_mass(v,m)
   print*,"The density is ",m/v
   call plus_equals(ell,j+3)
   print*,"ell is now",ell
   print*,"writing 354 in base 2"
   call base_write(354,2)

 contains

   integer function plus_plus(n)
    implicit none
    integer::n
    n = n+1
    print*,"ell = ",ell  ! within the scope of ell
    plus_plus = n
   end function plus_plus
    
  end program Aug02_2002

  integer function range(a,b)
   implicit none
   integer,intent(in)::a,b
   range = abs(a-b)
  end function range

  real function round(amount,n)
   implicit none
   integer,intent(in)::n
   real,intent(in)::amount
   integer,parameter::base = 10
   integer::factor
   factor = base**n
!    print*,"ell = ",ell  ! NOT within the scope of ell
   round = nint(amount*factor)/real(factor)
  end function round

  real function num_bac(initialpop,growthrate,time)
   implicit none
   real,intent(in)::initialpop,growthrate,time
   num_bac = initialpop*exp(growthrate*time)
  end function num_bac

  character function letter_grade(numericscore)
   implicit none
   integer,intent(in)::numericscore
   integer,parameter::minA = 90, minB = 80, minC = 70, minD = 60
   if(numericscore >= minA) then
    letter_grade = 'A'
   else if(numericscore >= minB) then
    letter_grade = 'B'
   else if(numericscore >= minC) then
    letter_grade = 'C'
   else if(numericscore >= minD) then
    letter_grade = 'D'
   else
    letter_grade = 'F'
   end if
  end function letter_grade

  recursive integer function gcd(a,b) result (g)
   implicit none
   integer,intent(in)::a,b
   if(a > b)then
    g = gcd(b,a)
   else if (a < 0) then
    g = gcd(-a,b)
   else if (a == 0) then
    g = b
   else
    g = gcd(mod(b,a),a)
   end if
  end function gcd

  integer function blank_count(word)
   implicit none
   character(*),intent(in)::word
   character,parameter::blank = " "
   integer::i
   blank_count = 0
   do i = 1,len(word) 
    if(word(i:i) == blank) blank_count = blank_count + 1
   end do
  end function blank_count

  subroutine get_volume_mass(volume,mass)
   implicit none
   real,intent(out)::volume,mass
   do
    print*,"Please enter the volume followed by the mass"
    read*,volume,mass
    if ((volume > 0) .and. (mass > 0)) exit
    print*,"Sorry, both volume and mass must be positive.  Please try again:"
   end do
  end subroutine get_volume_mass

  subroutine plus_equals(x,y)
!   adds y to x
   implicit none
   integer,intent(inout)::x
   integer,intent(in)::y
   x = x+y
  end subroutine plus_equals

  recursive subroutine base_write(number,base)
!  writes number in that base
   integer,intent(in)::number,base
!  input condition: base does not exceed 10
   print*,"SUBROUTINE base_write IS NOT AVAILABLE YET"
  end subroutine base_write