Date   : Sun, 22 Nov 2009 18:51:39 +0000
From   : jgh@... (Jonathan Graham Harston)
Subject: Detokeniser, was Quine

Try this code.
 
   10REM > DetokTest
   20REM Test detokiser
   30:
   40A%=PAGE:REPEAT
   50IFA%?1<>&FF:PRINTFNd(A%?2+256*A%?1,5);FNDetokenise($(A%+4)):A%=A%+A%?3
   60UNTILA%?1=&FF
   70END
   80:
   90DEFFNd(A%,N%)=RIGHT$("         "+STR$A%,N%)
  100:
  110GOTO 130
  120:
  130DEFFNDetokenise(A$):LOCAL A%,B%,C%,D%
  140tok%=tok%:IFtok%=0:tok%=&8000:REPEATtok%=tok%+1:UNTIL!tok%=&80444E41
  150B%=0:A%=0:REPEAT:A%=A%+1:C%=ASCMID$(A$,A%,1)
  160IFC%=34:B%=B%EOR1:VDU34:UNTILA%>=LENA$:=""
  170IFB%:VDUC%:UNTILA%>=LENA$:=""
  180IFC%=&F4:B%=&80
  190IFC%<128:VDUC%:UNTILA%>=LENA$:=""
  200IFC%=141:B%=ASCMID$(A$,A%+1,1):C%=ASCMID$(A$,A%+2,1):D%=ASCMID$(A$,A%+3,
1):PRINT;(C%AND63)+256*(D%AND63)+4*((B%AND&30)EOR&10)+&1000*((B%AND&C0)EOR&40)
;:B%=0:A%=A%+3:UNTILA%>=LENA$:=""
  210D%=tok%:REPEAT:B%=D%:REPEAT:D%=D%+1:UNTIL?D%>127:D%=D%+2
  220UNTILD%?-2=C%:REPEATVDU?B%:B%=B%+1:UNTIL?B%>127
  240B%=0:UNTILA%>=LENA$:=""
 
Also at http://mdfs.net/jgh/Develop/BBCBasic
 
I've been trying to develop a detokeniser library to compliment the
tokeniser routines at mdfs.net/blib, but the big problem with
detokenising is that the output string will almost always be longer
than the input string. That makes it difficult to return the
detokenised line as a string, as if the input string is 254 bytes
long with at least one token in it, the resultant string is going
to be longer than 255 characters.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
BBC IDE Hard Drive Interface - http://mdfs.net/Info/Comp/BBC/IDE