+
+;;; Unlike CMU CL, we represent the types FLOAT and REAL as
+;;; UNION-TYPEs of more primitive types, in order to make
+;;; type representation more unique, avoiding problems in the
+;;; simplification of things like
+;;; (subtypep '(or (single-float -1.0 1.0) (single-float 0.1))
+;;; '(or (real -1 7) (single-float 0.1) (single-float -1.0 1.0)))
+;;; When we allowed REAL to remain as a separate NUMERIC-TYPE,
+;;; it was too easy for the first argument to be simplified to
+;;; '(SINGLE-FLOAT -1.0), and for the second argument to be simplified
+;;; to '(OR (REAL -1 7) (SINGLE-FLOAT 0.1)) and then for the
+;;; SUBTYPEP to fail (returning NIL,T instead of T,T) because
+;;; the first argument can't be seen to be a subtype of any of the
+;;; terms in the second argument.
+;;;
+;;; The old CMU CL way was:
+;;; (!def-bounded-type float float nil)
+;;; (!def-bounded-type real nil nil)
+;;;
+;;; FIXME: If this new way works for a while with no weird new
+;;; problems, we can go back and rip out support for separate FLOAT
+;;; and REAL flavors of NUMERIC-TYPE. The new way was added in
+;;; sbcl-0.6.11.22, 2001-03-21.
+;;;
+;;; FIXME: It's probably necessary to do something to fix the
+;;; analogous problem with INTEGER and RATIONAL types. Perhaps
+;;; bounded RATIONAL types should be represented as (OR RATIO INTEGER).
+(defun coerce-bound (bound type inner-coerce-bound-fun)
+ (declare (type function inner-coerce-bound-fun))
+ (cond ((eql bound '*)
+ bound)
+ ((consp bound)
+ (destructuring-bind (inner-bound) bound
+ (list (funcall inner-coerce-bound-fun inner-bound type))))
+ (t
+ (funcall inner-coerce-bound-fun bound type))))
+(defun inner-coerce-real-bound (bound type)
+ (ecase type
+ (rational (rationalize bound))
+ (float (if (floatp bound)
+ bound
+ ;; Coerce to the widest float format available, to
+ ;; avoid unnecessary loss of precision:
+ (coerce bound 'long-float)))))
+(defun coerced-real-bound (bound type)
+ (coerce-bound bound type #'inner-coerce-real-bound))
+(defun coerced-float-bound (bound type)
+ (coerce-bound bound type #'coerce))
+(!def-type-translator real (&optional (low '*) (high '*))
+ (specifier-type `(or (float ,(coerced-real-bound low 'float)
+ ,(coerced-real-bound high 'float))
+ (rational ,(coerced-real-bound low 'rational)
+ ,(coerced-real-bound high 'rational)))))
+(!def-type-translator float (&optional (low '*) (high '*))
+ (specifier-type
+ `(or (single-float ,(coerced-float-bound low 'single-float)
+ ,(coerced-float-bound high 'single-float))
+ (double-float ,(coerced-float-bound low 'double-float)
+ ,(coerced-float-bound high 'double-float))
+ #!+long-float ,(error "stub: no long float support yet"))))
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