5 ms·

Editor-independent advice for working with Lisp

42 points by vog 16y ago

neonscribe 16y ago
The "killer feature" that Emacs brings is automatic indentation. Parenthesis matching is important, but an easy feature for non-progammable editors to support. Knowing how much whitespace belongs at the beginning of each line is harder, and pretty much requires programmability in the editor. Once you have had it, you will miss it when it is taken away. Manual indentation breaks your "flow" while composing code. This is true in C-like languages, but it is much more critical in Lisp, where there are fewer punctuation cues.
- aerique 16y ago
  No, the killer future that Emacs brings is Slime.
  - malkia 16y ago
    The killer feature is the editor knowing what's going on in the image. For example typing (blah - he can check from the current package - whether that's function, special symbol, etc. - and if it's in a table of specially formatted ones (if, when, unless, etc.) it can do better formatting. Not only that but you can inform about this in the actual. Same goes for Lispworks, and maybe for AllegroCL. Difference is emacs communicates with slime to the swanked image, and if that image hangs, your editor is still there - not the same with LispWorks and AllegroCL (but if you are careful, and know when it can explode then it's ok).
  - sedachv 16y ago
    SLIME is cool, but the underlying communications protocol (SWANK) is not only network transparent, but also editor-agnostic. Besides Emacs, it's also used by MCLIDE and the Cusp plugin for Eclipse.
- Xurinos 16y ago
  vim does automatic indention, too, fwiw. Although the author talked about manual shifting, he did not mention vim's "=". This is equivalent to emacs's default behavior for tab (for when emacs's automatic indention is bypassed). I agree with the other responder: slime. It is pretty much the only allure for me to emacs, and the only feature I really miss with current vim packages is the intellisense that understands what package I am working in, what new symbols I introduced. I am okay without, but I could probably work slightly faster if I had it.
- srean 16y ago
  Isn't this the feature that Steele and Stallman were working on, in Guy Steele's example of extreme pair programming. http://cycle-gap.blogspot.com/2007/09/extreme-pair-programming-guy-steele-and.html http://cycle-gap.blogspot.com/2007/09/extreme-pair-programmi...
neutronicus 16y ago
As an emacs user, one of the biggest contributors (other than SLIME method list prompts and the like) to my appreciation for Lisp is Paredit[1]. If you ever find yourself frustrated with counting parentheses, this is the thing for you. Essentially, it only adds delimiters in pairs - so you never delete closing parenthese, and provides functions for (| indicates cursor location)- 1. 'slurp' the token on either side of a list (|a b c) d -> (|a b c d) a (|b c d) -> (a |b c d) 2. 'barf' elements from either side of list (a |b c d) -> (a b c) d (a |b c d) -> a (b c d) 3. 'drill down' into nearest list (|a b c (d e f)) -> (a b c (|d e f)) 4. 'break out' of current list (a b c (d e |f)) -> (a b c |(d e f)) 5. And more, like 'jump across next list', 'delete next list', etc. Using any of these commands re-indents the code. It is the best method I have ever encountered in any language environment for doing 'code surgery' like placing existing code inside conditionals. I even use it for C (although it is not nearly as smart about C/C++ as it is about Lisp, so the benefit is not as great - c'est la vie. Perhaps one day I will attempt to hack decent C/C++ support into paredit). If I ever switch to vim, attempting to port paredit will be the first thing I do, and, if I fail, no switch. Well, that got long. Too bad the original poster on the newsgoup will never see this. [1] http://www.emacswiki.org/emacs/ParEdit http://www.emacswiki.org/emacs/ParEdit [2] 'slurp' and 'barf' are the "official" terminologies, by the way
- ScottBurson 16y ago
  Yes, this is the right way to edit Lisp. It gives most of the benefits of a structure editor without the downside. Balanced-delimiter editing makes Lisp actually easier to edit than any other language. (I've been editing Lisp this way since about 1980, when David Chapman and I implemented balanced-delimiter commands for Zmacs.) (BTW I'm sure Rob is aware of Paredit. He's been around comp.lang.lisp a long time.)
  - neutronicus 16y ago
    By, 'the original poster,' I meant the poster whose question Rob was answering. I guess that was unclear. I know he's a veteran!
fexl 16y ago
Can someone recommend a Lisp that will behave properly as a scripting language? By that I mean run quietly without a REPL, and honor this convention: #!/usr/bin/lisp
- pangram 16y ago
  Picolisp, although I suspect you can make a stub for most Lisps to get them to be usable in a shell script. Also, have you considered taking a look at SCSH, a Scheme shell? There's even a topic for it on the HN front page: http://news.ycombinator.com/item?id=2070891 http://news.ycombinator.com/item?id=2070891
- vog 16y ago
  Almost any Lisp implementation allows for starting your code as a stand-alone application. You may have to pass some interpreter option to your #! line, but that's all.
- sea6ear 16y ago
  I believe clisp will. see section 32.6.2. Scripting with CLISP in this document http://clisp.sourceforge.net/impnotes/quickstart.html http://clisp.sourceforge.net/impnotes/quickstart.html
  - fexl 16y ago
    Thanks for the suggestions everyone! I had a bad experience trying this with some Lisp a couple of years ago -- I could not for the life of me turn off the stupid banner printout, but I did manage to disable the REPL. At the time I just gave up and moved on, but I'll give it another try. The last time I actually programmed in Lisp was back in the mid-80s for my AI classes at GA Tech. I liked it then.
srean 16y ago
People complain about Lisp's parenthesis all the time. I almost never found them bothersome and this comes from a Lisp newbie. My editor is vim though, not emacs. The only occasion that parens have bothered me is when I have to read code printed on paper. Some code pieces are too beautiful to resist the temptation of taking a print out for a weekend reading, comment out bits with a pencil, scribble arrows all over it etc. Its then when I have to match tiny parens printed 2-up on a piece of paper that it gets frustrating, my eyes not being what they used to be (but I still print 2-up). A thought just occurred to me: maybe add a pretty printing mode to a2ps that draws the parens in different sizes and gray scale values. May be some day.

42 points by vog 16y ago

The "killer feature" that Emacs brings is automatic indentation. Parenthesis matching is important, but an easy feature for non-progammable editors to support. Knowing how much whitespace belongs at the beginning of each line is harder, and pretty much requires programmability in the editor. Once you have had it, you will miss it when it is taken away. Manual indentation breaks your "flow" while composing code. This is true in C-like languages, but it is much more critical in Lisp, where there are fewer punctuation cues.

aerique 16y ago
No, the killer future that Emacs brings is Slime.
- malkia 16y ago
  The killer feature is the editor knowing what's going on in the image. For example typing (blah - he can check from the current package - whether that's function, special symbol, etc. - and if it's in a table of specially formatted ones (if, when, unless, etc.) it can do better formatting. Not only that but you can inform about this in the actual. Same goes for Lispworks, and maybe for AllegroCL. Difference is emacs communicates with slime to the swanked image, and if that image hangs, your editor is still there - not the same with LispWorks and AllegroCL (but if you are careful, and know when it can explode then it's ok).
- sedachv 16y ago
  SLIME is cool, but the underlying communications protocol (SWANK) is not only network transparent, but also editor-agnostic. Besides Emacs, it's also used by MCLIDE and the Cusp plugin for Eclipse.
Xurinos 16y ago
vim does automatic indention, too, fwiw. Although the author talked about manual shifting, he did not mention vim's "=". This is equivalent to emacs's default behavior for tab (for when emacs's automatic indention is bypassed). I agree with the other responder: slime. It is pretty much the only allure for me to emacs, and the only feature I really miss with current vim packages is the intellisense that understands what package I am working in, what new symbols I introduced. I am okay without, but I could probably work slightly faster if I had it.
srean 16y ago
Isn't this the feature that Steele and Stallman were working on, in Guy Steele's example of extreme pair programming. http://cycle-gap.blogspot.com/2007/09/extreme-pair-programming-guy-steele-and.html http://cycle-gap.blogspot.com/2007/09/extreme-pair-programmi...

neutronicus 16y ago

As an emacs user, one of the biggest contributors (other than SLIME method list prompts and the like) to my appreciation for Lisp is Paredit[1]. If you ever find yourself frustrated with counting parentheses, this is the thing for you. Essentially, it only adds delimiters in pairs - so you never delete closing parenthese, and provides functions for (| indicates cursor location)- 1. 'slurp' the token on either side of a list (|a b c) d -> (|a b c d) a (|b c d) -> (a |b c d) 2. 'barf' elements from either side of list (a |b c d) -> (a b c) d (a |b c d) -> a (b c d) 3. 'drill down' into nearest list (|a b c (d e f)) -> (a b c (|d e f)) 4. 'break out' of current list (a b c (d e |f)) -> (a b c |(d e f)) 5. And more, like 'jump across next list', 'delete next list', etc. Using any of these commands re-indents the code. It is the best method I have ever encountered in any language environment for doing 'code surgery' like placing existing code inside conditionals. I even use it for C (although it is not nearly as smart about C/C++ as it is about Lisp, so the benefit is not as great - c'est la vie. Perhaps one day I will attempt to hack decent C/C++ support into paredit). If I ever switch to vim, attempting to port paredit will be the first thing I do, and, if I fail, no switch. Well, that got long. Too bad the original poster on the newsgoup will never see this. [1] http://www.emacswiki.org/emacs/ParEdit http://www.emacswiki.org/emacs/ParEdit [2] 'slurp' and 'barf' are the "official" terminologies, by the way

ScottBurson 16y ago
Yes, this is the right way to edit Lisp. It gives most of the benefits of a structure editor without the downside. Balanced-delimiter editing makes Lisp actually easier to edit than any other language. (I've been editing Lisp this way since about 1980, when David Chapman and I implemented balanced-delimiter commands for Zmacs.) (BTW I'm sure Rob is aware of Paredit. He's been around comp.lang.lisp a long time.)
- neutronicus 16y ago
  By, 'the original poster,' I meant the poster whose question Rob was answering. I guess that was unclear. I know he's a veteran!

fexl 16y ago

Can someone recommend a Lisp that will behave properly as a scripting language? By that I mean run quietly without a REPL, and honor this convention: #!/usr/bin/lisp

pangram 16y ago
Picolisp, although I suspect you can make a stub for most Lisps to get them to be usable in a shell script. Also, have you considered taking a look at SCSH, a Scheme shell? There's even a topic for it on the HN front page: http://news.ycombinator.com/item?id=2070891 http://news.ycombinator.com/item?id=2070891
vog 16y ago
Almost any Lisp implementation allows for starting your code as a stand-alone application. You may have to pass some interpreter option to your #! line, but that's all.
sea6ear 16y ago
I believe clisp will. see section 32.6.2. Scripting with CLISP in this document http://clisp.sourceforge.net/impnotes/quickstart.html http://clisp.sourceforge.net/impnotes/quickstart.html
- fexl 16y ago
  Thanks for the suggestions everyone! I had a bad experience trying this with some Lisp a couple of years ago -- I could not for the life of me turn off the stupid banner printout, but I did manage to disable the REPL. At the time I just gave up and moved on, but I'll give it another try. The last time I actually programmed in Lisp was back in the mid-80s for my AI classes at GA Tech. I liked it then.

srean 16y ago

People complain about Lisp's parenthesis all the time. I almost never found them bothersome and this comes from a Lisp newbie. My editor is vim though, not emacs. The only occasion that parens have bothered me is when I have to read code printed on paper. Some code pieces are too beautiful to resist the temptation of taking a print out for a weekend reading, comment out bits with a pencil, scribble arrows all over it etc. Its then when I have to match tiny parens printed 2-up on a piece of paper that it gets frustrating, my eyes not being what they used to be (but I still print 2-up). A thought just occurred to me: maybe add a pretty printing mode to a2ps that draws the parens in different sizes and gray scale values. May be some day.