C GMMM 10
C ..................................................................GMMM 20
C GMMM 30
C SUBROUTINE GMMMA GMMM 40
C GMMM 50
C PURPOSE GMMM 60
C COMPUTES THE GAMMA FUNCTION FOR A GIVEN ARGUMENT GMMM 70
C GMMM 80
C USAGE GMMM 90
C CALL GMMMA(XX,GX,IER) GMMM 100
C GMMM 110
C DESCRIPTION OF PARAMETERS GMMM 120
C XX -THE ARGUMENT FOR THE GAMMA FUNCTION GMMM 130
C GX -THE RESULTANT GAMMA FUNCTION VALUE GMMM 140
C IER-RESULTANT ERROR CODE WHERE GMMM 150
C IER=0 NO ERROR GMMM 160
C IER=1 XX IS WITHIN .000001 OF BEING A NEGATIVE INTEGER GMMM 170
C IER=2 XX GT 57, OVERFLOW, GX SET TO 1.0E75 GMMM 180
C GMMM 190
C REMARKS GMMM 200
C NONE GMMM 210
C GMMM 220
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED GMMM 230
C NONE GMMM 240
C GMMM 250
C METHOD GMMM 260
C THE RECURSION RELATION AND POLYNOMIAL APPROXIMATION GMMM 270
C BY C.HASTINGS,JR., 'APPROXIMATIONS FOR DIGITAL COMPUTERS', GMMM 280
C PRINCETON UNIVERSITY PRESS, 1955 GMMM 290
C GMMM 300
C ..................................................................GMMM 310
C GMMM 320
SUBROUTINE GMMMA(XX,GX,IER) GMMM 330
IF(XX-57.)6,6,4 GMMM 340
4 IER=2 GMMM 350
GX=1.7E38 GMMM 360
RETURN GMMM 370
6 X=XX GMMM 380
ERR=1.0E-6 GMMM 390
IER=0 GMMM 400
GX=1.0 GMMM 410
IF(X-2.0)50,50,15 GMMM 420
10 IF(X-2.0)110,110,15 GMMM 430
15 X=X-1.0 GMMM 440
GX=GX*X GMMM 450
GO TO 10 GMMM 460
50 IF(X-1.0)60,120,110 GMMM 470
C GMMM 480
C SEE IF X IS NEAR NEGATIVE INTEGER OR ZERO GMMM 490
C GMMM 500
60 IF(X-ERR)62,62,80 GMMM 510
62 Y=FLOAT(INT(X))-X GMMM 520
IF(ABS(Y)-ERR)130,130,64 GMMM 530
64 IF(1.0-Y-ERR)130,130,70 GMMM 540
C GMMM 550
C X NOT NEAR A NEGATIVE INTEGER OR ZERO GMMM 560
C GMMM 570
70 IF(X-1.0)80,80,110 GMMM 580
80 GX=GX/X GMMM 590
X=X+1.0 GMMM 600
GO TO 70 GMMM 610
110 Y=X-1.0 GMMM 620
GY=1.0+Y*(-0.5771017+Y*(+0.9858540+Y*(-0.8764218+Y*(+0.8328212+ GMMM 630
1Y*(-0.5684729+Y*(+0.2548205+Y*(-0.05149930))))))) GMMM 640
GX=GX*GY GMMM 650
120 RETURN GMMM 660
130 IER=1 GMMM 670
RETURN GMMM 680
END GMMM 690