New subject: XRM 78: Add lazy and/or evaluation at the meta-level.

19 Jun 2006


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"SIGOURE" == SIGOURE Benoit sigoure.benoit@lrde.epita.fr writes:
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https://svn.lrde.epita.fr/svn/xrm/trunk
Index: ChangeLog
from  SIGOURE Benoit  sigoure.benoit@lrde.epita.fr
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Add lazy and/or evaluation at the meta-level.
   One can now rely on laziness of logical operators to prevent what
   could be an error at the meta-level, eg: x > 0 & s[x-1]=0
Brilliant, thanks!
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eval-meta-code =
     eval-meta-if

<+ lazy-eval-and
<+ lazy-eval-or
<+ unroll-meta-for
<+ unroll-meta-forin
<+ (expand-pformulas; eval-meta-code) // try again on expansed code.

@@ -72,6 +81,26 @@
         end
       end
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lazy-eval-and =
?|[ e1 & e2 ]|
; <prism-desugar> e1
; try(LitToBool) => e1'
; if !e1' => False() then
   !False()


 else


   fail


 end



lazy-eval-or =
?|[ e1 | e2 ]|
; <prism-desugar> e1
; try(LitToBool) => e1'
; if !e1' => True() then
   !True()


 else


   fail


 end



I'm surprised not to see some code removed: I believe you are already
handling things such as "true & e" elsewhere.

    

Re: XRM 78: Add lazy and/or evaluation at the meta-level.