Subj : Re: Something strange going on. To : Thomas Lake From : Johann Klasek - swap last two domai Date : Mon Jun 04 2018 09:57:58 Thomas Lake wrote: > On Wednesday, April 11, 2018 at 6:33:17 AM UTC-4, 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. > > You SHOULD get a syntax error. Commodore (Microsoft) BASIC is supposed to only allow numeric constants, not variables after GOTO and GOSUB. What do you actually see happening? Not exactly how BASIC V2 parses it. GOTO parses all digits (ignoring blanks everywhere in between) and stops a the first non-digit character. In this case GOTO stops right before the FN token. So, the parsed line number is empty. The fallback (evaluation) for an empty line number argument is 0. Therefore GOTO jumps to line 0 and starts over. As others suggested already, one should use ON GOTO ... to use a calculated form of GOTO, or using a patched GOTO, or using the display containing a prepared GOTO statement with keyboard buffer ... could go like this 100 PRINT "{CLRSCR}{DOWN}{DOWN}GOTO "500+500"{HOME}"; 110 POKE631,13: REM RETURN INTO KEYBOARD BUFFER 120 POKE198.1: REM KEYBOARD BUFFER LENGTH 130 END: REM HERE 1000 PRINT "WE REACHED LINE 1000" Johann --- SoupGate-Win32 v1.05 * Origin: Agency HUB, Dunedin - New Zealand | Fido<>Usenet Gateway (3:770/3) .