On Wednesday, April 11, 2018 at 12:33:17 PM UTC+2, Shaun Bebbington wrote:   
   > Hi,   
   >   
   > I found something odd today in the powerful CBM BASIC v2.0.   
   >   
   > Having worked with Sinclair BASIC quite a lot recently, I use GOTO X where X   
   is a valid line number (i.e., LET X = 100). But I know that's not possible with   
    Microsoft BASIC. Of course there is the ON X GO TO 100,200 ...   
   >   
   > So I thought "I know, I'll try and use a function, could CBM BASIC use this   
   as a look up table". The following, I expected to go to the value in the   
   function A() which returns 10, but...   
   >   
   > 0 DEF FN A(X) = 10   
   > 1 PRINT FN A(0)   
   > 2 GO TO FN A(0)   
   > 3 PRINT "END GRACEFULLY"   
   > 4 END   
   > 10 PRINT "STOP"   
   > 11 STOP   
   >   
   > Try it for yourself. What's going on here?   
   >   
   > Thanks in advance.   
   >   
   > Shaun.   
      
   I went the "hard" way and traced what happens using VICE's monitor's 'z'   
   command. I recommend that you do the same, consulting a commented BASIC ROM   
   listing if necessary.   
   But there's a much easier way to get the idea: Let your programs start at line   
   1 instead of 0.   
      
   Chris   
      
   Edit: The above should read "Let your programs start _with_ line number 1".   
   Here's a short version of the "hard" way:   
   - Start x64 from a console window (otherwise breakpoints might not work)   
   - Enter a one-liner "0 goto 0"   
   - RUN the one-liner   
   - Enter VICE's monitor (Ctrl-h)   
   - Enter 'bk a971' in VICE's monitor   
   - Enter 'x' in VICE's monitor   
   - Not(ic)e that the C-flag is set but every other time the breakpoint is   
   reached   
      
   Now repeat the above procedure, but let your one-liner be "0 goto a" instead   
   this time. Note that the C-flag is set _all_ the time.   
      
   --- SoupGate-Win32 v1.05   
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