C LEPS 10
C ..................................................................LEPS 20
C LEPS 30
C SUBROUTINE LEPS LEPS 40
C LEPS 50
C PURPOSE LEPS 60
C COMPUTES THE VALUE OF AN N-TERM EXPANSION IN LEGENDRE LEPS 70
C POLYNOMIALS WITH COEFFICIENT VECTOR C FOR ARGUMENT VALUE X. LEPS 80
C LEPS 90
C USAGE LEPS 100
C CALL LEPS(Y,X,C,N) LEPS 110
C LEPS 120
C DESCRIPTION OF PARAMETERS LEPS 130
C Y - RESULT VALUE LEPS 140
C X - ARGUMENT VALUE LEPS 150
C C - COEFFICIENT VECTOR OF GIVEN EXPANSION LEPS 160
C COEFFICIENTS ARE ORDERED FROM LOW TO HIGH LEPS 170
C N - DIMENSION OF COEFFICIENT VECTOR C LEPS 180
C LEPS 190
C REMARKS LEPS 200
C OPERATION IS BYPASSED IN CASE N LESS THAN 1 LEPS 210
C LEPS 220
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED LEPS 230
C NONE LEPS 240
C LEPS 250
C METHOD LEPS 260
C DEFINITION LEPS 270
C Y=SUM(C(I)*P(I-1,X), SUMMED OVER I FROM 1 TO N). LEPS 280
C EVALUATION IS DONE BY MEANS OF UPWARD RECURSION LEPS 290
C USING THE RECURRENCE EQUATION FOR LEGENDRE POLYNOMIALS LEPS 300
C P(N+1,X)=2*X*P(N,X)-P(N-1,X)-(X*P(N,X)-P(N-1,X))/(N+1). LEPS 310
C LEPS 320
C ..................................................................LEPS 330
C LEPS 340
SUBROUTINE LEPS(Y,X,C,N) LEPS 350
C LEPS 360
DIMENSION C(1) LEPS 370
C LEPS 380
C TEST OF DIMENSION LEPS 390
IF(N)1,1,2 LEPS 400
1 RETURN LEPS 410
C LEPS 420
2 Y=C(1) LEPS 430
IF(N-2)1,3,3 LEPS 440
C LEPS 450
C INITIALIZATION LEPS 460
3 H0=1. LEPS 470
H1=X LEPS 480
C LEPS 490
DO 4 I=2,N LEPS 500
H2=X*H1 LEPS 510
H2=H2-H0+H2-(H2-H0)/FLOAT(I) LEPS 520
H0=H1 LEPS 530
H1=H2 LEPS 540
4 Y=Y+C(I)*H0 LEPS 550
RETURN LEPS 560
END LEPS 570