Re: problem with trailing comment in repl
On Fri 11 Feb 2011 22:15, "Jose A. Ortega Ruiz" writes: > scheme@(guile-user)> (define a 3) ;; foo > <- cursor stays here; no prompt > > is that intended? i'm hoping it is not, because it confuses geiser, who > is waiting for a new prompt to mark the end of the transaction. It would be nice if there were a prompt in this case. However, it is difficult to do. Because this case is very much like: guile> (define a 3) ( <- no prompt, waiting for you to finish the expression Or indeed, like: guile> ;; foo <- no prompt After reading an expression, the REPL reader flushes any available whitespace, then goes into a new read. If there are characters waiting on the current input port, as they are if there is more than one expression on one line, no prompt is printed. In this case we flush the whitespace, and start reading at the ";", and keep on reading in the next line. Regards, Andy -- http://wingolog.org/
Re: problem with trailing comment in repl
On Sat, Feb 12 2011, Andy Wingo wrote: > On Fri 11 Feb 2011 22:15, "Jose A. Ortega Ruiz" writes: > >> scheme@(guile-user)> (define a 3) ;; foo >> <- cursor stays here; no prompt >> >> is that intended? i'm hoping it is not, because it confuses geiser, who >> is waiting for a new prompt to mark the end of the transaction. > > It would be nice if there were a prompt in this case. However, it is > difficult to do. Because this case is very much like: > >guile> (define a 3) ( ><- no prompt, waiting for you to finish the expression > > Or indeed, like: >guile> ;; foo ><- no prompt > > After reading an expression, the REPL reader flushes any available > whitespace, then goes into a new read. If there are characters waiting > on the current input port, as they are if there is more than one > expression on one line, no prompt is printed. In this case we flush the > whitespace, and start reading at the ";", and keep on reading in the > next line. I'm not sure i understand this reasoning, because when there are two (or more) complete sexps in a line they're accepted, and a new prompt appears; and the same happens for a sexp with trailing whitespace, and i was expecting a comment to be equivalent to whitespace. But, anyway, you know better than me how the reader works and i'm sure there are good reasons for that behaviour. (And of course it is true that the case of _only_ whitespace behaves as the one of only a comment.) However, i think there's a problem with metacommands at the "non-prompt": scheme@(guile-user)> ;; foo ,error While compiling expression: Syntax error: standard input:2:0: unquote: expression not valid outside of quasiquote in form (unquote error) scheme@(guile-user)> This happens with all metacommands i've tried, not just ,error. Compare to: scheme@(guile-user)> ,error Nothing to debug. scheme@(guile-user)> Cheers, jao -- Convictions are more dangerous enemies of truth than lies. -Friedrich Wilhelm Nietzsche, philosopher (1844-1900)
Re: problem with trailing comment in repl
On Sat 12 Feb 2011 14:21, "Jose A. Ortega Ruiz" writes: > I'm not sure i understand this reasoning, because when there are two (or > more) complete sexps in a line they're accepted, and a new prompt > appears; Of course. 1. Guile: No input available, print prompt: guile> 2. User: one line of input: (exp-1) (exp-2) 3. Guile: read one sexp 4. Guile: flush whitespace; input state is: (exp-2) 5. Guile: Input is ready, so don't print prompt, just read 6. Guile: Flush whitespace, no input available, so print prompt: guile > i was expecting a comment to be equivalent to whitespace. We could add some hacks in that regard, but it wouldn't work for ecmascript... If there is input, Guile calls `read', not some hypothetical `read-syntax' that could return a comment, and `read' doesn't return until it has read an entire expression. > However, i think there's a problem with metacommands at the > "non-prompt": > > scheme@(guile-user)> ;; foo > ,error > While compiling expression: > Syntax error: Meta-commands have to be the first thing on the prompt. It's a special case to look for the comma character; once we've seen non-whitespace -- ";" in this case -- we're in the scheme reader, not the repl reader. Regards, Andy -- http://wingolog.org/
Re: problem with trailing comment in repl
Hello all, I was thinking about how this might be solved. I can see two ways of doing it: - The nicer way: add a new read function (or a keyword argument to the current read function) that can tell it to stop without returning anything if it hits a newline and there's no more input ready on its port. You'd probably have to have it return a special "no expression" token, but you could make that with an uninterned symbol. - The quicker way: if the language in use is scheme, change the next-char function (repl.scm line 205) to know about comments, so that if it saw a semicolon, it would snarf everything until the end of the line. Either way is language-specific, but I don't think that's really avoidable since different languages have different comment syntaxes. Either way could also lead to a situation where some languages (i.e. Scheme) had the nice prompt-printing functionality and others didn't, but again, I think that's to be expected if this has to be implemented once per language. What do you all think of these ideas? Noah On Sat, Feb 12, 2011 at 9:36 AM, Andy Wingo wrote: > On Sat 12 Feb 2011 14:21, "Jose A. Ortega Ruiz" writes: > >> I'm not sure i understand this reasoning, because when there are two (or >> more) complete sexps in a line they're accepted, and a new prompt >> appears; > > Of course. > > 1. Guile: No input available, print prompt: > guile> > > 2. User: one line of input: > (exp-1) (exp-2) > > 3. Guile: read one sexp > > 4. Guile: flush whitespace; input state is: > (exp-2) > > 5. Guile: Input is ready, so don't print prompt, just read > > 6. Guile: Flush whitespace, no input available, so print prompt: > guile > >> i was expecting a comment to be equivalent to whitespace. > > We could add some hacks in that regard, but it wouldn't work for > ecmascript... If there is input, Guile calls `read', not some > hypothetical `read-syntax' that could return a comment, and `read' > doesn't return until it has read an entire expression. > >> However, i think there's a problem with metacommands at the >> "non-prompt": >> >> scheme@(guile-user)> ;; foo >> ,error >> While compiling expression: >> Syntax error: > > Meta-commands have to be the first thing on the prompt. It's a special > case to look for the comma character; once we've seen non-whitespace -- > ";" in this case -- we're in the scheme reader, not the repl reader. > > Regards, > > Andy > -- > http://wingolog.org/ > >
Re: problem with trailing comment in repl
Hi Noah, I think it makes sense to have a reader that actually returns comments. That, to me, is the general solution: the REPL reader just treats a comment as whitespace. On Sun 13 Feb 2011 16:22, Noah Lavine writes: > - The quicker way: if the language in use is scheme, change the > next-char function (repl.scm line 205) to know about comments, so that > if it saw a semicolon, it would snarf everything until the end of the > line. Nasty, but a good idea I think! Care to submit a patch? :) Andy -- http://wingolog.org/
Re: problem with trailing comment in repl
The attached patch does it. I almost hate to commit it because it's such a hack, but this is from my last Guile session: scheme@(guile-user)> 'foo $2 = foo scheme@(guile-user)> 'foo ; hi there! $3 = foo scheme@(guile-user)> ; why, hello! scheme@(guile-user)> ,q Noah On Sun, Feb 13, 2011 at 2:19 PM, Andy Wingo wrote: > Hi Noah, > > I think it makes sense to have a reader that actually returns comments. > That, to me, is the general solution: the REPL reader just treats a > comment as whitespace. > > On Sun 13 Feb 2011 16:22, Noah Lavine writes: > >> - The quicker way: if the language in use is scheme, change the >> next-char function (repl.scm line 205) to know about comments, so that >> if it saw a semicolon, it would snarf everything until the end of the >> line. > > Nasty, but a good idea I think! Care to submit a patch? :) > > Andy > -- > http://wingolog.org/ > 0001-Show-prompts-after-a-comment-in-the-REPL.patch Description: Binary data
Re: problem with trailing comment in repl
Hi! Noah Lavine writes: > The attached patch does it. I almost hate to commit it because it's > such a hack, but this is from my last Guile session: > > scheme@(guile-user)> 'foo > $2 = foo > scheme@(guile-user)> 'foo ; hi there! > $3 = foo > scheme@(guile-user)> ; why, hello! > scheme@(guile-user)> ,q Nice! Can you add a test case? Thanks, Ludo’.
Re: problem with trailing comment in repl
Hello, > Nice! Can you add a test case? I've thought about it, and I'm not sure how to do it well. The trouble is that this only applies to the REPL, not scripts. So a test would have to wrap the REPL in something and make sure its output is right. I might be able to do that, but if I just compared the output to the string I expected, the test would fail if the output format changed at all, which seems excessively fragile to me. And I'm not sure how to test it otherwise, because the REPL catches exceptions, so I can't just run the REPL and see if it throws one. Could someone help me? Thanks, Noah
Re: problem with trailing comment in repl
On Sun 13 Feb 2011 22:27, Noah Lavine writes: > The attached patch does it. I almost hate to commit it because it's > such a hack, but this is from my last Guile session: > > scheme@(guile-user)> 'foo > $2 = foo > scheme@(guile-user)> 'foo ; hi there! > $3 = foo > scheme@(guile-user)> ; why, hello! > scheme@(guile-user)> ,q It was a hack, in both the good and bad senses of the word ;-) I ended up pushing something similar. Let me know how it goes. Regards, Andy -- http://wingolog.org/
