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From: koft@elbereth.rutgers.edu (Dan Koft)
Newsgroups: comp.lang.c
Subject: Calling IMSL routines (FORTRAN) from C
Keywords: C, IMSL, FORTRAN
Message-ID: <May.29.12.00.35.1991.16903@elbereth.rutgers.edu>
Date: 29 May 91 16:00:38 GMT
Organization: Rutgers Univ., New Brunswick, N.J.
Lines: 66


Please help me if you can.  I have a C program that I want to call an
IMSL routine called QDAGI, the code in FORTRAN looks like:

	CALL QDAGI(F, BOUND, INTERV, ERRABS, ERRREL, RESULT, ERREST)

Where (from the IMSL manual):
F      - User supplied function to be integrated.  The form is F(X),
	 where: X - Independant variable (Input), F - The function
	 value (Output).  F must be declared EXTERNAL in the calling
	 program.
BOUND  - Finite bound of the integration range (Input). Ignored if
	 INTERV=2.
INTERV - Flag indicating integration range (Input). If INTERV is -1
	 the interval is -infinity to BOUND; if 1, BOUND to +infinity;
	 if 2 -infinity to +infinity.
ERRABS - Absolute accuracy desired (Input).
ERRREL - Relative accuracy desired (Input).
RESULT - Estimate of the integral from A to B of F (Output).
ERREST - Estimate of the absolute value of the error (Output).

I have tried all the ways I could think of to call this function
without proper results.  Below is the test program from the IMSL
manual as I have translated it to C.

#include <stdio.h>
#include <math.h>
#define Abs(x) ( (x)>0? (x) : (-x))
double F(double x);
 
extern void qdagi(double *F(), double *bound, int *interv, double *errabs,
                  double *errel, double *result, double *errest);
main()
{ 
double abs,bound,errabs,errest,error,errrel,exact,ppi,result;

int interv = 1;
bound = 0.0;
errabs = 0.0;
errrel = 0.001;

qdagi((&)F(),&bound,&interv,&errabs,&errrel,&result,&errest);
/* The above line is where I believe the problem lies*/

ppi = 3.1415926;
exact = -ppi * log(10.)/20.;
error = Abs(result - exact);
printf(" Computed = %8.3f           exact = %8.3f\nError ", result, exact);
printf("estimate = %f error = %f\n", errest, error);
}
 
double F(double x)
{
  double temp;
  temp = log(x)/(1. + pow((10. * x),2.0));
  return temp;
}
 
-- 

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Dan Koft				Email: koft@elbereth.rutgers.edu
RU-CS, Rutgers University		      {backbone}!rutgers!elbereth!koft
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