... Also note that with fix form text in positions 73 to 80 was considered to be a comment. ... PROGRAM TEST_ADAPTIVE_QUAD IMPLICIT NONE INTERFACE FUNCTION F(X) RESULT ( FUNCTION _VALUE) REAL , INTENT (IN) :: X REAL :: FUNCTION _VALUE END FUNCTION F END INTERFACE INTERFACE RECURSIVE FUNCTION ADAPTIVE_QUAD (F, A, B, TOL, ABS_ ERROR ) RESULT ( RESULT ) REAL , EXTERNAL :: F REAL , INTENT (IN) :: A, B, TOL REAL , INTENT (OUT) :: ABS_ ERROR REAL :: RESULT ...