Fortran Fortran: Integrating Different Functions

[porkpie]

Hi!
Im using fortran and am trying to create a integrating program that is able to use different functions.

I have written the subroutine that will integrate but would also like it to be able to use different functions determine by user selection.

Here is my subroutine:
subroutine comptrap
implicit none
double precision h,f,f1,f2,x,x1,x2,int
double precision func1
integer n,i
print*, 'Enter x1, the lower boundary.'
read*, x1
print*, 'Enter x2, the upper boundary.'
read*,x2
print*, 'Enter the number of intervals, n.'
read*, n
h=(x2-x1)/n
int=0
do i=1,(n-1)

x=x1+(h*i)
f=func1(x)
print*, f
int=int+f
end do
f1=func1(x1)
f2=func1(x2)
int=h*(int+(f1+f2)/2)


print*, f1,f2,'Integral=',int,h
end subroutine

And an example of a function:
double precision function func1(x)
implicit none
double precision x
func1=x**2
end

If anyone could advise me on how to program it to allow a function to be picked for integration that that would be great.

Thanks in advance.

 

[DrClaude]

Add an argument to func1 to specify which function to integrate, then in func1 put only a select case to call the function that will contain the desired function definition.