SLATEC Routines --- E1 ---

*DECK E1
      FUNCTION E1 (X)
C***BEGIN PROLOGUE  E1
C***PURPOSE  Compute the exponential integral E1(X).
C***LIBRARY   SLATEC (FNLIB)
C***CATEGORY  C5
C***TYPE      SINGLE PRECISION (E1-S, DE1-D)
C***KEYWORDS  E1 FUNCTION, EXPONENTIAL INTEGRAL, FNLIB,
C             SPECIAL FUNCTIONS
C***AUTHOR  Fullerton, W., (LANL)
C***DESCRIPTION
C
C E1 calculates the single precision exponential integral, E1(X), for
C positive single precision argument X and the Cauchy principal value
C for negative X.  If principal values are used everywhere, then, for
C all X,
C
C    E1(X) = -Ei(-X)
C or
C    Ei(X) = -E1(-X).
C
C
C Series for AE11       on the interval -1.00000D-01 to  0.
C                                        with weighted error   1.76E-17
C                                         log weighted error  16.75
C                               significant figures required  15.70
C                                    decimal places required  17.55
C
C
C Series for AE12       on the interval -2.50000D-01 to -1.00000D-01
C                                        with weighted error   5.83E-17
C                                         log weighted error  16.23
C                               significant figures required  15.76
C                                    decimal places required  16.93
C
C
C Series for E11        on the interval -4.00000D+00 to -1.00000D+00
C                                        with weighted error   1.08E-18
C                                         log weighted error  17.97
C                               significant figures required  19.02
C                                    decimal places required  18.61
C
C
C Series for E12        on the interval -1.00000D+00 to  1.00000D+00
C                                        with weighted error   3.15E-18
C                                         log weighted error  17.50
C                        approx significant figures required  15.8
C                                    decimal places required  18.10
C
C
C Series for AE13       on the interval  2.50000D-01 to  1.00000D+00
C                                        with weighted error   2.34E-17
C                                         log weighted error  16.63
C                               significant figures required  16.14
C                                    decimal places required  17.33
C
C
C Series for AE14       on the interval  0.          to  2.50000D-01
C                                        with weighted error   5.41E-17
C                                         log weighted error  16.27
C                               significant figures required  15.38
C                                    decimal places required  16.97
C
C***REFERENCES  (NONE)
C***ROUTINES CALLED  CSEVL, INITS, R1MACH, XERMSG
C***REVISION HISTORY  (YYMMDD)
C   770701  DATE WRITTEN
C   890531  Changed all specific intrinsics to generic.  (WRB)
C   891115  Modified prologue description.  (WRB)
C   891115  REVISION DATE from Version 3.2
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C   900315  CALLs to XERROR changed to CALLs to XERMSG.  (THJ)
C   920618  Removed space from variable names.  (RWC, WRB)
C***END PROLOGUE  E1