 
      FUNCTION E1(X)
C***BEGIN PROLOGUE  E1
C***DATE WRITTEN   770701   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  C5
C***KEYWORDS  E1,EXPONENTIAL INTEGRAL,SPECIAL FUNCTION
C***AUTHOR  FULLERTON, W., (LANL)
C***PURPOSE  Computes the exponential integral E1(X).
C***DESCRIPTION
C
C E1(X) calculates the single precision exponential integral
C for positive, single precision argument X.  It returns the
C Cauchy principal value for negative X.  If principal values are
C used everywhere, then for all X
C
C     EI(X) = -E1(-X)
C or
C     E1(X) = -EI(-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***REFERENCES  (NONE)
C***ROUTINES CALLED  CSEVL,INITS,R1MACH,XERROR
C***END PROLOGUE  E1
 
 
