REAL FUNCTION R1MACH(I)
C***BEGIN PROLOGUE  R1MACH
C***DATE WRITTEN   790101   (YYMMDD)
C***REVISION DATE  831014   (YYMMDD)
C***CATEGORY NO.  R1
C***KEYWORDS  MACHINE CONSTANTS
C***AUTHOR  FOX, P. A., (BELL LABS)
C           HALL, A. D., (BELL LABS)
C           SCHRYER, N. L., (BELL LABS)
C***PURPOSE  Returns single precision machine dependent constants
C***DESCRIPTION
C
C     R1MACH can be used to obtain machine-dependent parameters
C     for the local machine environment.  It is a function
C     subroutine with one (input) argument, and can be called
C     as follows, for example
C
C          A = R1MACH(I)
C
C     where I=1,...,5.  The (output) value of A above is
C     determined by the (input) value of I.  The results for
C     various values of I are discussed below.
C
C  Single-Precision Machine Constants
C  R1MACH(1) = B**(EMIN-1), the smallest positive magnitude.
C  R1MACH(2) = B**EMAX*(1 - B**(-T)), the largest magnitude.
C  R1MACH(3) = B**(-T), the smallest relative spacing.
C  R1MACH(4) = B**(1-T), the largest relative spacing.
C  R1MACH(5) = LOG10(B)
C***REFERENCES  FOX, P.A., HALL, A.D., SCHRYER, N.L, *FRAMEWORK FOR
C                 A PORTABLE LIBRARY*, ACM TRANSACTIONS ON MATHE-
C                 MATICAL SOFTWARE, VOL. 4, NO. 2, JUNE 1978,
C                 PP. 177-188.
C***ROUTINES CALLED  XERROR
C***END PROLOGUE  R1MACH