[cl-json-devel] Encoding DOUBLE-FLOAT

[Robert Goldman]

On 6/25/11 Jun 25 -1:24 AM, Boris Smilga wrote:
> On Fri, Jun 24, 2011 at 2:23 AM, Robert Goldman <rpgoldman at sift.info> wrote:
> 
>> I was going to compare, e.g., MOST-POSITIVE-SHORT-FLOAT,
>> LEAST-NEGATIVE-SHORT-FLOAT and MOST-POSITIVE-SINGLE-FLOAT,
>> LEAST-NEGATIVE-SINGLE-FLOAT (at compile time) to attempt to determine if
>> SHORT-FLOAT and SINGLE-FLOAT are the same on the current implementation
>> and possibly conditionally-compile away the SINGLE-FLOAT type, and
>> similarly for DOUBLE- and LONG-....
>>
>> I would not be checking the numeric values of the number at run-time,
>> but the bounds on the types at compile time.  Would that not work?
> 
> Ah, yes, now I see.  But then you might just write it
> straightforwardly as (subtypep 'short-float 'single-float), or vice
> versa.  Since subtypes of float are either disjoint or synonymous,
> subtypep in this context effectively tests the types for equality.
> 
> Still, I doubt the intended effect is worth the trouble.  Having
> superfluous clauses in typecase is explicitly allowed: ‘[...] is
> permissible for more than one clause to specify a matching type’ (CLHS
> 5.3, definition of TYPECASE et al.)  In fact, by trying to get rid of
> them beforehand we would be (re)doing the compiler's job.   E. g., CCL
> eliminates them right there at macro expansion time:
> 
> (macroexpand
>  '(typecase foo
>     (short-float #\S) (long-float #\L) (single-float #\F) (double-float #\D)))
> ⇒ (LET ((#:G4 FOO))
>     (DECLARE (IGNORABLE #:G4))
>     (COND ((TYPEP #:G4 'SHORT-FLOAT) NIL #\S)
>           ((TYPEP #:G4 'LONG-FLOAT) NIL #\L)))
> 
> Are we going to such lengths just in order to get rid of annoying
> warnings in a single implementation?

Yes.  If these were simply style warnings, then I would agree with you.
 However, they are not --- they are real, bona fide warnings, causing
COMPILE-FILE failure:

;Compiler warnings for "home:lisp;cl-json;src;encoder.lisp.newest" :
;   In WRITE-JSON-NUMBER: Clause (SINGLE-FLOAT 'SINGLE-FLOAT) ignored in
ETYPECASE form - shadowed by (SHORT-FLOAT 'SHORT-FLOAT) .
;   In WRITE-JSON-NUMBER: Clause (LONG-FLOAT 'LONG-FLOAT) ignored in
ETYPECASE form - shadowed by (DOUBLE-FLOAT 'DOUBLE-FLOAT) .
; Warning: COMPILE-FILE warned while performing #<COMPILE-OP (:FORCE T)
#x3020009CEB4D> on #<CL-SOURCE-FILE "cl-json" "src" "encoder">.
; While executing: #<STANDARD-METHOD ASDF:PERFORM (ASDF:COMPILE-OP
ASDF:CL-SOURCE-FILE)>, in process repl-thread(10).
; Warning: COMPILE-FILE failed while performing #<COMPILE-OP (:FORCE T)
#x3020009CEB4D> on #<CL-SOURCE-FILE "cl-json" "src" "encoder">.
; While executing: #<STANDARD-METHOD ASDF:PERFORM (ASDF:COMPILE-OP
ASDF:CL-SOURCE-FILE)>, in process repl-thread(10).


So I think these warnings must die.

I am inclined to think that these should simply be STYLE-WARNINGs, but
CCL does not agree with me.

Best,
r