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C                                                               C
C               F  O R T  _ F C N . F                           C
C                                                               C
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C
C  The following Fortran code is used to illustrate a simple FORTRAN
C  function and its unit test driver.
C 
C  Note: We use the Pre-processor to handle the #defines and 
C        coditional Compilation.
C

C
C Uncomment the following #define if you want DEBUG info.
C
/* #define DEBUG */

C
C Define an output file name
C

#define  OUTFILE     'fout.dat'          /* Fortran Data Output File */
#define  NPTS        3

  
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C  								C
C UNIT Test driver to test the function fort_fcn		C
C								C
C Standalone main program to test routine: 'fort_fcn'		C
C								C
C Parameter: 							C
C								C
C								C
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#ifdef UNIT_TEST

      PROGRAM FUNIT_TEST
      REAL   PARAM1
      INTEGER  UNIT
  

 
      UNIT   = 6

      write(6,*)'------------- FORTRAN UNIT TEST ROUTINE -----------'
      write(6,*)'Unit Testing the Fortran fcn with parameter: ',UNIT
      write(6,*) ''

C
C    Call the subroutine being tested with a variety of arguments
C      
      PARAM1 = FORT_FCN( UNIT)

      write(6,*)'Fortran function returned: ',PARAM1
      write(6,*) ''

      END
#endif



C
C Here is the only function in this the file
C 
  
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C  								C
C FUNCTION FORT_FCN      					C
C								C
C Test function to illustrate FORTRAN code			C
C								C
C Parameter: 							C
C								C
C    index - The unit where the output should go   		C
C								C
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      REAL FUNCTION FORT_FCN( index )                 
      INTEGER index  
      REAL *8 x(NPTS)

C/*
C * Write some stuff to the ouput unit specified in the calling sequence. 
C */ 

      x(1) = 666
      write(index,*)'-------------'
      write(index,*)'Entering the Fortran function with parameter: ',index
      write(index,*) ''      
     
C/*
C * Here's a swatch of debugging code hidden behind the pre-processor 
C * directive 'DEBUG'. If this
C * directive is set with '#define DEBUG' or set on the compiler command line with
C * the flag '-DDEBUG' , then this code will become active. 
C */
 
#ifdef DEBUG
C/*
C * Here is some debugging code...It writes to the standard output ( Device 6 )
C * Note: There's nothing assigned to the array 'x' so this will print junk
C *       if you turn on DEBUG.
C */

 500  CONTINUE 
      write(6,*)'' 
      write(6,*)'Debugging in FORTRAN Function: '
      write(6,*)'----------------------' 
      DO 510 loop  = 1, NPTS
        write(6,*) x(i) 
510  CONTINUE 

#endif

C
C  Finally we return a value through the function name
C
      FORT_FCN = 666.0
      RETURN

      END