home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Frostbyte's 1980s DOS Shareware Collection
/
floppyshareware.zip
/
floppyshareware
/
DOOG
/
PCSSP1.ZIP
/
AGLGQUAD.ZIP
/
DQA4.FOR
< prev
next >
Wrap
Text File
|
1985-11-29
|
2KB
|
53 lines
C
C ..................................................................
C
C SUBROUTINE DQA4
C
C PURPOSE
C TO COMPUTE INTEGRAL(EXP(-X)*FCT(X)/SQRT(X), SUMMED OVER X
C FROM 0 TO INFINITY).
C
C USAGE
C CALL DQA4 (FCT,Y)
C PARAMETER FCT REQUIRES AN EXTERNAL STATEMENT
C
C DESCRIPTION OF PARAMETERS
C FCT - THE NAME OF AN EXTERNAL DOUBLE PRECISION FUNCTION
C SUBPROGRAM USED.
C Y - THE RESULTING DOUBLE PRECISION INTEGRAL VALUE.
C
C REMARKS
C NONE
C
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
C THE EXTERNAL DOUBLE PRECISION FUNCTION SUBPROGRAM FCT(X)
C MUST BE FURNISHED BY THE USER.
C
C METHOD
C EVALUATION IS DONE BY MEANS OF 4-POINT GENERALIZED GAUSS-
C LAGUERRE QUADRATURE FORMULA, WHICH INTEGRATES EXACTLY
C WHENEVER FCT(X) IS A POLYNOMIAL UP TO DEGREE 7.
C FOR REFERENCE, SEE
C SHAO/CHEN/FRANK, TABLES OF ZEROS AND GAUSSIAN WEIGHTS OF
C CERTAIN ASSOCIATED LAGUERRE POLYNOMIALS AND THE RELATED
C GENERALIZED HERMITE POLYNOMIALS, IBM TECHNICAL REPORT
C TR00.1100 (MARCH 1964), PP.15-16.
C
C ..................................................................
C
SUBROUTINE DQA4(FCT,Y)
C
C
DOUBLE PRECISION X,Y,FCT
C
X=.8588635689012034D1
Y=.39920814442273524D-3*FCT(X)
X=.39269635013582872D1
Y=Y+.34155966014826951D-1*FCT(X)
X=.13390972881263614D1
Y=Y+.41560465162978376D0*FCT(X)
X=.14530352150331709D0
Y=Y+.13222940251164826D1*FCT(X)
RETURN
END