Mercurial > octave-nkf
annotate libcruft/slatec-fn/atanh.f @ 7948:af10baa63915 ss-3-1-50
3.1.50 snapshot
author | John W. Eaton <jwe@octave.org> |
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date | Fri, 18 Jul 2008 17:42:48 -0400 |
parents | 82be108cc558 |
children | d17237256856 |
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1 *DECK ATANH |
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2 FUNCTION ATANH (X) |
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3 C***BEGIN PROLOGUE ATANH |
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4 C***PURPOSE Compute the arc hyperbolic tangent. |
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5 C***LIBRARY SLATEC (FNLIB) |
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6 C***CATEGORY C4C |
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7 C***TYPE SINGLE PRECISION (ATANH-S, DATANH-D, CATANH-C) |
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8 C***KEYWORDS ARC HYPERBOLIC TANGENT, ATANH, ELEMENTARY FUNCTIONS, |
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9 C FNLIB, INVERSE HYPERBOLIC TANGENT |
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10 C***AUTHOR Fullerton, W., (LANL) |
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11 C***DESCRIPTION |
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12 C |
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13 C ATANH(X) computes the arc hyperbolic tangent of X. |
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14 C |
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15 C Series for ATNH on the interval 0. to 2.50000D-01 |
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16 C with weighted error 6.70E-18 |
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17 C log weighted error 17.17 |
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18 C significant figures required 16.01 |
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19 C decimal places required 17.76 |
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20 C |
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21 C***REFERENCES (NONE) |
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22 C***ROUTINES CALLED CSEVL, INITS, R1MACH, XERMSG |
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23 C***REVISION HISTORY (YYMMDD) |
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24 C 770401 DATE WRITTEN |
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25 C 890531 Changed all specific intrinsics to generic. (WRB) |
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26 C 890531 REVISION DATE from Version 3.2 |
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27 C 891214 Prologue converted to Version 4.0 format. (BAB) |
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28 C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ) |
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29 C 900326 Removed duplicate information from DESCRIPTION section. |
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30 C (WRB) |
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31 C***END PROLOGUE ATANH |
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32 DIMENSION ATNHCS(15) |
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33 LOGICAL FIRST |
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34 SAVE ATNHCS, NTERMS, DXREL, SQEPS, FIRST |
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35 DATA ATNHCS( 1) / .0943951023 93195492E0 / |
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36 DATA ATNHCS( 2) / .0491984370 55786159E0 / |
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37 DATA ATNHCS( 3) / .0021025935 22455432E0 / |
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38 DATA ATNHCS( 4) / .0001073554 44977611E0 / |
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39 DATA ATNHCS( 5) / .0000059782 67249293E0 / |
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40 DATA ATNHCS( 6) / .0000003505 06203088E0 / |
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41 DATA ATNHCS( 7) / .0000000212 63743437E0 / |
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42 DATA ATNHCS( 8) / .0000000013 21694535E0 / |
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43 DATA ATNHCS( 9) / .0000000000 83658755E0 / |
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44 DATA ATNHCS(10) / .0000000000 05370503E0 / |
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45 DATA ATNHCS(11) / .0000000000 00348665E0 / |
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46 DATA ATNHCS(12) / .0000000000 00022845E0 / |
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47 DATA ATNHCS(13) / .0000000000 00001508E0 / |
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48 DATA ATNHCS(14) / .0000000000 00000100E0 / |
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49 DATA ATNHCS(15) / .0000000000 00000006E0 / |
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50 DATA FIRST /.TRUE./ |
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51 C***FIRST EXECUTABLE STATEMENT ATANH |
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52 IF (FIRST) THEN |
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53 NTERMS = INITS (ATNHCS, 15, 0.1*R1MACH(3)) |
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54 DXREL = SQRT (R1MACH(4)) |
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55 SQEPS = SQRT (3.0*R1MACH(3)) |
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56 ENDIF |
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57 FIRST = .FALSE. |
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58 C |
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59 Y = ABS(X) |
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60 IF (Y .GE. 1.0) CALL XERMSG ('SLATEC', 'ATANH', 'ABS(X) GE 1', 2, |
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61 + 2) |
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62 C |
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63 IF (1.0-Y .LT. DXREL) CALL XERMSG ('SLATEC', 'ATANH', |
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64 + 'ANSWER LT HALF PRECISION BECAUSE ABS(X) TOO NEAR 1', 1, 1) |
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65 C |
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66 ATANH = X |
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67 IF (Y.GT.SQEPS .AND. Y.LE.0.5) ATANH = X*(1.0 + CSEVL (8.*X*X-1., |
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68 1 ATNHCS, NTERMS)) |
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69 IF (Y.GT.0.5) ATANH = 0.5*LOG((1.0+X)/(1.0-X)) |
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70 C |
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71 RETURN |
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72 END |