Viivi 00.09 release notes

Version 00.09.00 has been improved at the following points compared to the previous version 00.08.00.

• Improved in showing error information.


• Changed algorithm of some parts in processing macros.


• More kinds of Unicode-character can be used in symbols/strings.
  Symbol-characters like '●' and '■', together with rule-characters, etc., are now available.


• An option to accept direct expressions for some objects is introduced.

  You can directly specify some objects in the S-expressions, using a command-line option

  	-D N
  				

  or a procedure call

  	(viivi-set! direct-input-objects N)
  				

  where

  	N is a bit-summation of 1,2, and 4.
  				

  • 1  ...  to accept direct-expressions for the built-in objects

    	(ex.) #<procedure:let>   ; built-in procedure let
    	      #<procedure:cos>   ; built-in procedure cos
    	      #<constant:PI>     ; Viivi-extension constant PI
    				and so on.
    						

  • 2  ...  to accept direct-expressions for the unspecified value

    	     #<unspecified>
    						

  • 4  ...  to accept direct-expressions for a NIL

    	     #<nil>
    						

  The main purpose of introducing this option is as follows:

  • a. To specify built-in procedures (and constants) directly independent of symbol bindings.
    
    Viivi had known problems, that a built-in procedure becomes unavailable forever when the symbol representing it is re-bound to another value at the top-level, or that, as the following example shows, when the symbol representing a built-in procedure is re-bound to another value after the definition of a closure which utilized the built-in procedure, then the behavior becomes changed from that expected.

    	1> (define (func arg) (if arg 100 200))  ; a closure definition
    	2> (func #t)         ; gives 100.  No problem.
    	3> (define if list)  ; when 'if' is overwritten
    	4> (func #t)         ; gives (#t 100 200).  Should it be 100?
    						

    In such a case, the direct-input for the built-in procedure 'if' provides the work-around:

    	1> (define (func arg) (#<procedure:if> arg 100 200))
    			     ; directly specified 'if' procedure
    	2> (func #t)         ; gives 100.  No problem.
    	3> (define if list)  ; even when 'if' is overwritten
    	4> (func #t)         ; still gives 100 as expected
    						

    You can recover the original binding that has been modified at the top-level, as well:

    	1> (define cos -)
    	2> (cos 30)    ; --> -30   'cos' became '-'!
    	3> (define cos #<procedure:cos>)    ; recovery
    	4> (cos 30)    ; --> 0.15425144988758405
    		       ; back to the original behavior of cos
    						

  • b. To use an output from an interpreter in the form as it is for the input to another interpreter (But this feature is still in preparation and needs some improvements).



• Small bug fixes.