;;
;;     This is the CMLIB version of I1MACH, the integer machine
;;     constants subroutine originally developed for the PORT library.
;;
;;     I1MACH can be used to obtain machine-dependent parameters
;;     for the local machine environment.  It is a function
;;     subroutine with one (input) argument, and can be called
;;     as follows, for example
;;
;;          K = I1MACH(I)
;;
;;     where I=1,...,16.  The (output) value of K above is
;;     determined by the (input) value of I.  The results for
;;     various values of I are discussed below.
;;
;;  I/O unit numbers.
;;    I1MACH( 1) = the standard input unit.
;;    I1MACH( 2) = the standard output unit.
;;    I1MACH( 3) = the standard punch unit.
;;    I1MACH( 4) = the standard error message unit.
;;
;;  Words.
;;    I1MACH( 5) = the number of bits per integer storage unit.
;;    I1MACH( 6) = the number of characters per integer storage unit.
;;
;;  Integers.
;;    assume integers are represented in the S-digit, base-A form
;;
;;               sign ( X(S-1)*A**(S-1) + ... + X(1)*A + X(0) )
;;
;;               where 0 .LE. X(I) .LT. A for I=0,...,S-1.
;;    I1MACH( 7) = A, the base.
;;    I1MACH( 8) = S, the number of base-A digits.
;;    I1MACH( 9) = A**S - 1, the largest magnitude.
;;
;;  Floating-Point Numbers.
;;    Assume floating-point numbers are represented in the T-digit,
;;    base-B form
;;               sign (B**E)*( (X(1)/B) + ... + (X(T)/B**T) )
;;
;;               where 0 .LE. X(I) .LT. B for I=1,...,T,
;;               0 .LT. X(1), and EMIN .LE. E .LE. EMAX.
;;    I1MACH(10) = B, the base.
;;
;;  Single-Precision
;;    I1MACH(11) = T, the number of base-B digits.
;;    I1MACH(12) = EMIN, the smallest exponent E.
;;    I1MACH(13) = EMAX, the largest exponent E.
;;
;;  Double-Precision
;;    I1MACH(14) = T, the number of base-B digits.
;;    I1MACH(15) = EMIN, the smallest exponent E.
;;    I1MACH(16) = EMAX, the largest exponent E.
(defun i1mach (i)
  (ecase i
     ;; The standard input unit
    (1 0)
     ;; The standard output unit
    (2 1)
     ;; The standard punch unit
    (3 3)
     ;; The standard error message unit
    (4 2)

     ;; The number of bits per integer storage unit.  What does this
     ;; mean in Lisp?
    #+nil
    (5 (integer-length most-positive-fixnum))
    ;; The number of characters per integer storage unit.  What does
    ;; this mean in Lisp?
    #+nil
    (6 1)

    ;; The base of integers.  Assume 2's complement
    (7 2)
    ;; The number of base-2 digits.  Assume fixnum size?
    (8 (integer-length most-positive-fixnum))
    ;; The largest magnitude
    (9 most-positive-fixnum)

    ;; Base of floating-poing representation
    (10 (float-radix 1f0))
    ;; Number of digits in representation
    (11 (float-digits 1f0))
    ;; Smallest exponent
    (12 (multiple-value-bind (frac exp sign)
	    (decode-float least-positive-normalized-single-float)
	  (declare (ignore frac sign))
	  (+ exp 1)))
    ;; Largest exponent
    (13 (multiple-value-bind (frac exp sign)
	    (decode-float most-positive-single-float)
	  (declare (ignore frac sign))
	  (- exp 1)))
    ;; Same for double-precision
    (14 (float-digits 1d0))
    (15 (multiple-value-bind (frac exp sign)
	    (decode-float least-positive-normalized-double-float)
	  (declare (ignore frac sign))
	  (+ exp 1)))
    (16 (multiple-value-bind (frac exp sign)
	    (decode-float most-positive-double-float)
	  (declare (ignore frac sign))
	  (- exp 1)))
))