[parenscript-devel] [PATCH] Define bit-shifting special forms >> and <<, and ASH as a macro.

[Vladimir Sedach]

Hi Scott,

Thanks for the patch. I've applied it against the current changes and pushed.

One thing I didn't do is export << and >> special forms, just ash.
What do you think about that?

Vladimir

2010/10/29  <sblist at me.com>:
> I'm not sure how you feel about adding >> and << as special forms, but
> this seems to allow for a simpler implementation of ASH since it needs
> to do some higher-level transformations such as optimizing forms with a
> a constant COUNT argument along with avoiding multiple evaluation.
>
>        Scott
>
> ---
>  src/macros.lisp        |   14 ++++++++++++++
>  src/package.lisp       |    4 ++++
>  src/printer.lisp       |    2 +-
>  src/special-forms.lisp |    4 +++-
>  4 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/src/macros.lisp b/src/macros.lisp
> index 2014330..2c0c295 100644
> --- a/src/macros.lisp
> +++ b/src/macros.lisp
> @@ -59,6 +59,20 @@
>
>  (define-ps-symbol-macro pi (getprop *math '*pi*))
>
> +(defpsmacro ash (integer count)
> +  (let ((count (ps-macroexpand count)))
> +    (cond ((and (numberp count) (> count 0)) `(<< ,integer ,count))
> +          ((numberp count) `(>> ,integer ,(- count)))
> +          ((complex-js-expr? count)
> +           (let ((count-var (ps-gensym)))
> +             `(let ((,count-var ,count))
> +                (if (> ,count-var 0)
> +                    (<< ,integer ,count-var)
> +                    (>> ,integer (- ,count-var))))))
> +          (t `(if (> ,count 0)
> +                  (<< ,integer ,count)
> +                  (>> ,integer (- ,count)))))))
> +
>  ;;; Types
>
>  (defpsmacro stringp (x)
> diff --git a/src/package.lisp b/src/package.lisp
> index 7921a37..92922e7 100644
> --- a/src/package.lisp
> +++ b/src/package.lisp
> @@ -99,6 +99,10 @@
>    #:logxor
>    #:lognot
>
> +   #:ash
> +   #:>>
> +   #:<<
> +
>    #:*
>    #:/
>    #:rem
> diff --git a/src/printer.lisp b/src/printer.lisp
> index 73df146..5f119b7 100644
> --- a/src/printer.lisp
> +++ b/src/printer.lisp
> @@ -169,7 +169,7 @@ vice-versa.")
>  (defprinter js:post-- (x)
>   (ps-print x)"--")
>
> -(defprinter (js:+ js:- js:* js:/ js:% js:&& js:\|\| js:& js:\| js:-= js:+= js:*= js:/= js:%= js:^ js:&= js:^= js:\|= js:= js:== js:=== js:!== js:in js:!= js:> js:>= js:< js:<=)
> +(defprinter (js:+ js:- js:* js:/ js:% js:&& js:\|\| js:& js:\| js:-= js:+= js:*= js:/= js:%= js:^ js:&= js:^= js:\|= js:= js:== js:=== js:!== js:in js:!= js:> js:>= js:< js:<= js:<< js:>>)
>     (&rest args)
>   (loop for (arg . remaining) on args do
>        (print-op-argument op arg)
> diff --git a/src/special-forms.lisp b/src/special-forms.lisp
> index 6633b2f..5ca7a52 100644
> --- a/src/special-forms.lisp
> +++ b/src/special-forms.lisp
> @@ -25,7 +25,9 @@
>     logior     js:\|
>     logxor     js:^
>     lognot     js:~
> -    ;; todo: ash for shifts
> +
> +    >>         js:>>
> +    <<         js:<<
>
>     throw      js:throw
>     array      js:array
> --
> 1.7.2.1
>
>
>
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