C DNPS 10
C ..................................................................DNPS 20
C DNPS 30
C SUBROUTINE DCNPS DNPS 40
C DNPS 50
C PURPOSE DNPS 60
C COMPUTES THE VALUE OF AN N-TERM EXPANSION IN CHEBYSHEV DNPS 70
C POLYNOMIALS WITH COEFFICIENT VECTOR C FOR ARGUMENT VALUE X. DNPS 80
C DNPS 90
C USAGE DNPS 100
C CALL DCNPS(Y,X,C,N) DNPS 110
C DNPS 120
C DESCRIPTION OF PARAMETERS DNPS 130
C Y - RESULT VALUE DNPS 140
C DOUBLE PRECISION VARIABLE DNPS 150
C X - ARGUMENT VALUE DNPS 160
C DOUBLE PRECISION VARIABLE DNPS 170
C C - COEFFICIENT VECTOR OF GIVEN EXPANSION DNPS 180
C COEFFICIENTS ARE ORDERED FROM LOW TO HIGH DNPS 190
C DOUBLE PRECISION VECTOR DNPS 200
C N - DIMENSION OF COEFFICIENT VECTOR C DNPS 210
C DNPS 220
C REMARKS DNPS 230
C OPERATION IS BYPASSED IN CASE N LESS THAN 1 DNPS 240
C DNPS 250
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED DNPS 260
C NONE DNPS 270
C DNPS 280
C METHOD DNPS 290
C DEFINITION DNPS 300
C Y=SUM(C(I)*T(I-1,X), SUMMED OVER I FROM 1 TO N). DNPS 310
C EVALUATION IS DONE BY MEANS OF BACKWARD RECURSION DNPS 320
C USING THE RECURRENCE EQUATION FOR CHEBYSHEV POLYNOMIALS DNPS 330
C T(N+1,X)=2*X*T(N,X)-T(N-1,X). DNPS 340
C DNPS 350
C ..................................................................DNPS 360
C DNPS 370
SUBROUTINE DCNPS(Y,X,C,N) DNPS 380
C DNPS 390
DIMENSION C(1) DNPS 400
DOUBLE PRECISION C,Y,X,H0,H1,H2,ARG DNPS 410
C DNPS 420
C TEST OF DIMENSION DNPS 430
IF(N)1,1,2 DNPS 440
1 RETURN DNPS 450
C DNPS 460
2 IF(N-2)3,4,4 DNPS 470
3 Y=C(1) DNPS 480
RETURN DNPS 490
C DNPS 500
C INITIALIZATION DNPS 510
4 ARG=X+X DNPS 520
H1=0.D0 DNPS 530
H0=0.D0 DNPS 540
C DNPS 550
DO 5 I=1,N DNPS 560
K=N-I DNPS 570
H2=H1 DNPS 580
H1=H0 DNPS 590
5 H0=ARG*H1-H2+C(K+1) DNPS 600
Y=0.5D0*(C(1)-H2+H0) DNPS 610
RETURN DNPS 620
END DNPS 630