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Commit | Line | Data |
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21886bb6 | 1 | * |
2 | * $Id$ | |
3 | * | |
4 | * $Log$ | |
5 | * Revision 1.1.1.2 1996/10/30 08:28:27 cernlib | |
6 | * Version 7.04 | |
7 | * | |
8 | * Revision 1.1.1.1 1996/04/12 15:29:22 plothow | |
9 | * Version 7.01 | |
10 | * | |
11 | * | |
12 | #include "pdf/pilot.h" | |
13 | C | |
14 | C .................................................................. | |
15 | C | |
16 | C SUBROUTINE GAMMADO | |
17 | C | |
18 | C PURPOSE | |
19 | C COMPUTES THE GAMMADO FUNCTION FOR A GIVEN ARGUMENT | |
20 | C | |
21 | C USAGE | |
22 | C CALL GAMMADO(XX,GX,IER) | |
23 | C | |
24 | C DESCRIPTION OF PARAMETERS | |
25 | C XX -THE ARGUMENT FOR THE GAMMADO FUNCTION | |
26 | C GX -THE RESULTANT GAMMADO FUNCTION VALUE | |
27 | C IER-RESULTANT ERROR CODE WHERE | |
28 | C IER=0 NO ERROR | |
29 | C IER=1 XX IS WITHIN .000001 OF BEING A NEGATIVE INTEGER | |
30 | C IER=2 XX GT 34.5, OVERFLOW, GX SET TO 1.0E38 | |
31 | C | |
32 | C REMARKS | |
33 | C NONE | |
34 | C | |
35 | C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED | |
36 | C NONE | |
37 | C | |
38 | C METHOD | |
39 | C THE RECURSION RELATION AND POLYNOMIAL APPROXIMATION | |
40 | C BY C.HASTINGS,JR., 'APPROXIMATIONS FOR DIGITAL COMPUTERS', | |
41 | C PRINCETON UNIVERSITY PRESS, 1955 | |
42 | C | |
43 | C .................................................................. | |
44 | C | |
45 | SUBROUTINE GAMMADO(XX,GX,IER) | |
46 | IF(XX-34.5)6,6,4 | |
47 | 4 IER=2 | |
48 | GX=1.E38 | |
49 | RETURN | |
50 | 6 X=XX | |
51 | ERR=1.0E-6 | |
52 | IER=0 | |
53 | GX=1.0 | |
54 | IF(X-2.0)50,50,15 | |
55 | 10 IF(X-2.0)110,110,15 | |
56 | 15 X=X-1.0 | |
57 | GX=GX*X | |
58 | GO TO 10 | |
59 | 50 IF(X-1.0)60,120,110 | |
60 | C | |
61 | C SEE IF X IS NEAR NEGATIVE INTEGER OR ZERO | |
62 | C | |
63 | 60 IF(X-ERR)62,62,80 | |
64 | 62 Y=FLOAT(INT(X))-X | |
65 | IF(ABS(Y)-ERR)130,130,64 | |
66 | 64 IF(1.0-Y-ERR)130,130,70 | |
67 | C | |
68 | C X NOT NEAR A NEGATIVE INTEGER OR ZERO | |
69 | C | |
70 | 70 IF(X-1.0)80,80,110 | |
71 | 80 GX=GX/X | |
72 | X=X+1.0 | |
73 | GO TO 70 | |
74 | 110 Y=X-1.0 | |
75 | GY=1.0+Y*(-0.5771017+Y*(+0.9858540+Y*(-0.8764218+Y*(+0.8328212+ | |
76 | 1Y*(-0.5684729+Y*(+0.2548205+Y*(-0.05149930))))))) | |
77 | GX=GX*GY | |
78 | 120 RETURN | |
79 | 130 IER=1 | |
80 | RETURN | |
81 | END |