Getting an unclassifiable statement error in Fortran 95

[ngendler]

Getting an "unclassifiable statement" error in Fortran 95

I am trying to integrate the function x from 0 to 1. Here is my code:

program myownmonte
!This program will integrate the function x from 0 to 1
implicit none
real :: ans0,y,f,x,xmax
integer :: icount,nmax,i,iseed
iseed = 89237
call srand(iseed)

nmax = 100000

icount = 0
xmax = 1
ans0 = 0
do i=1,nmax
x = rand()
y = rand()
f = f(x)
if (y.le.f) then
icount = icount + 1
end if
ans0 = ans0 + f(x)
end do
print *, icount/nmax,ans0/nmax
end program myownmonte



function f(x)
implicit none
real :: x,f
f = x
end function f

And here are the errors I'm getting:

f = f(x)
1
Error: Unclassifiable statement at (1)
mymonte.f95:21:

ans0 = ans0 + f(x)
1
Error: Unclassifiable statement at (1)

Could someone help me fix this, and kindly let me know what the phrase "unclassifiable statement" means? Thanks in advance!

 

[SteamKing]

In your main program, you have a variable 'f' and also a function 'f'. You can't have both in the same program unit. Rename either the variable or the function.

 

[ngendler]

@SteamKing, that didn't work. When I remove f from my list of reals, I get another error saying that f has no implicit type, which makes me think that I need it to be declared as real.

 

[phyzguy]

SteamKing is still right that using f as both a function and a variable is the problem. The statement:

f = f(x)

really makes no sense, since you are trying to use the same symbol as a variable and a function. Your attempt to fix it wasn't correct, since you need to tell the compiler what kind of datatype f is. You need to do something like this. This will compile and run.


program myownmonte
!This program will integrate the function x from 0 to 1
implicit none
real :: ans0,y,f,fx,x,xmax
integer :: icount,nmax,i,iseed
iseed = 89237
call srand(iseed)

nmax = 100000

icount = 0
xmax = 1
ans0 = 0
do i=1,nmax
x = rand()
y = rand()
fx = f(x)
if (y.le.fx) then
icount = icount + 1
end if
ans0 = ans0 + fx
end do
print *, icount/nmax,ans0/nmax
end program myownmonte



function f(x)
implicit none
real :: x,f
f = x
end function f

 

[SteamKing]

'Rename' and 'remove' mean different things, in English at least.