On 2018-08-04, at 09:21:14, Charles Mills wrote: > > The HLASM team's dance card is already pretty full but you can certainly > picture something like that in HLASM: > > J *+3I > > Meaning "here + 3 instructions." 'I' is perhaps not the best indicator > because it is easily confused with a digit, although J *+n seldom ends in a > legitimate 1. > > Yes, the assembler would have to do look-ahead. Yes, HLASM would have to > impose some limits and caveats. > > I'm not crazy about it. It solves the "what if the instruction length > changes, such as from A to AG?" problem, but not the "what if someone > hastily and with inadequate thought inserts or deletes an instruction?" > problem. > Knuth's scheme wasn't relative bytes, nor instructions, nor even source code lines. It was an actual coded label with very local scope. No hazard from inserting instructions.
> -----Original Message----- > From: Peter Relson > Sent: Saturday, August 4, 2018 7:23 AM > >> "This isn't a 'real' branch-that is, we aren't going very far..." > > Donald Knuth's assembler, which we had available in college in the 70's, > had the concept of a "relative label". > I can't remember if there was one name pattern for "forward" and one for > "backward" or whether you couldn't use it for "backward". It avoided > (IIRC, the former.) > unnecessarily unreadable label names, and avoided the uniqueness problem. > And when used properly (i.e., well within a "screen" amout) it was > perfectly clear. > And hardly needed cross-reference. -- gil
