Product Type Trapezoidal Integration

TOMS436 is a FORTRAN77 library which implements ACM TOMS algorithm 436, which carries out a product type trapezoidal integration to estimate the integral from A to B of F(X) * G(X).

While the text of many ACM TOMS algorithms is available online through ACM: or NETLIB:, most of the early algorithms are not available. This is one of them. I typed it in.


call ptrap ( a, b, n, fn, gn, vint )
where A and B are the left and right endpoints of the interval, N is the number of times the rule is to be compounded, FN and GN are external functions for evaluating the integrand factors, and VINT is returned as the estimated value of the integral of FN(X) * GN(X) from A to B.


TOMS436 is available in a FORTRAN77 version.

Related Data and Programs:

INTLIB, a FORTRAN90 library which estimates integrals.

QUADRULE, a FORTRAN90 library which can define various quadrature rules to estimate integrals.

TEST_INT, a FORTRAN90 library which contains routines defining a number of scalar functions of to test routines that estimate integrals.

TOMS437, a FORTRAN77 library which carries out product type Simpson's integration.

TOMS438, a FORTRAN77 library which carries out product type two-point Gauss-Legendre-Simpson's integration.

TOMS439, a FORTRAN77 library which carries out product type three-point Gauss-Legendre-Simpson's integration.


  1. Robert Boland,
    Algorithm 436: Product Type Trapezoidal Integration,
    Communications of the ACM,
    Volume 15, Number 12, December 1972, page 1070.

Source Code:

Examples and Tests:

List of Routines:

You can go up one level to the FORTRAN77 source codes.

Last revised on 05 December 2005.