RE: Unnest your mess with 'and'
Hi Erik Thanks for writing this awesome article, your humour made it a very joyful read! I actually found that technique myself too, and used it in certain cases, its just perfect when you have multiple sequential things to do but you want to cancel execution when one of it fails. When using this technique, one is actually not interested in the return value of (and), just in the fact that it evaluates its arguments one after another and stops when it gets NIL the first time. I think this is fully in the spirit of PicoLisp and you will get an extra skill point in Software Surgery for using it. I actually didn't realise this was something to tell the mailing list, but it absolutely is, thank you for caring and for your time, Erik! Extra points for the telling wording and illustration. Cheers and claps, beneroth - Original Message - From: Erik Gustafson [mailto:erik.d.gustaf...@gmail.com] To: picolisp@software-lab.de Sent: Sat, 22 Aug 2015 13:29:00 -0500 Subject: Hi list, I was thinking about some of the things brought up in the last thread, 'The `if-let` construct', notably Mike's comment about certain idioms being useless within the PicoLisp feature set. Now I like Clojure's '-' just as much as the next Clojure enthusiast, but I agree we don't need it in PicoLisp. I wrote a little tutorial explaining how we can use 'and' to accomplish the same thing as '-' and friends. It can be found here, https://github.com/erdg/learning-picolisp/blob/master/unnest-your-mess-with-and.md What do you all think of this technique? Any feedback would be great. I plan to add a bunch more mini-tutorials to this repo in the coming months to help those new to the language start to feel more at home. Cheers, Erik
RE: Unnest your mess with 'and'
Of course you can also use (or) to achieve the opposite - stop when a call or evaluation returns something (not NIL). This way you have actually a very cheap implementation of the Design Pattern (GoF) 'chain of responsibility', when one function successfully handles the required case, stop there, else try the next function. Here too you can see the baffling elegance of PicoLisp: Regenaxer surely had this usage of (or) in mind as (or) returns the result of the last expression, and not merely T which would limit its usability a lot. Maybe you should mention the appliance of this technique with (or) at the end of article. - Original Message - From: andr...@itship.ch [mailto:andr...@itship.ch] To: picolisp@software-lab.de Sent: Sat, 22 Aug 2015 21:11:45 +0200 Subject: Hi Erik Thanks for writing this awesome article, your humour made it a very joyful read! I actually found that technique myself too, and used it in certain cases, its just perfect when you have multiple sequential things to do but you want to cancel execution when one of it fails. When using this technique, one is actually not interested in the return value of (and), just in the fact that it evaluates its arguments one after another and stops when it gets NIL the first time. I think this is fully in the spirit of PicoLisp and you will get an extra skill point in Software Surgery for using it. I actually didn't realise this was something to tell the mailing list, but it absolutely is, thank you for caring and for your time, Erik! Extra points for the telling wording and illustration. Cheers and claps, beneroth - Original Message - From: Erik Gustafson [mailto:erik.d.gustaf...@gmail.com] To: picolisp@software-lab.de Sent: Sat, 22 Aug 2015 13:29:00 -0500 Subject: Hi list, I was thinking about some of the things brought up in the last thread, 'The `if-let` construct', notably Mike's comment about certain idioms being useless within the PicoLisp feature set. Now I like Clojure's '-' just as much as the next Clojure enthusiast, but I agree we don't need it in PicoLisp. I wrote a little tutorial explaining how we can use 'and' to accomplish the same thing as '-' and friends. It can be found here, https://github.com/erdg/learning-picolisp/blob/master/unnest-your-mess-with-and.md What do you all think of this technique? Any feedback would be great. I plan to add a bunch more mini-tutorials to this repo in the coming months to help those new to the language start to feel more at home. Cheers, Erik
Re: Unnest your mess with 'and'
Hey Beneroth, Thanks for the kind words, my pleasure to share with you all. Of course you can also use (or) to achieve the opposite - stop when a call or evaluation returns something (not NIL). This way you have actually a very cheap implementation of the Design Pattern (GoF) 'chain of responsibility', when one function successfully handles the required case, stop there, else try the next function. Maybe you should mention the appliance of this technique with (or) at the end of article. Great idea, I might just make that a sister article, so to speak. I want to keep these as short as possible, something one could work through in 15 min or so. Alex Williams also has a nice snippet on using (or) this way in the EXPLAIN.md of his 'picolisp-json' lib. When using this technique, one is actually not interested in the return value of (and), just in the fact that it evaluates its arguments one after another and stops when it gets NIL the first time. Right, I'll make a note of that when I get a chance to update, along with any other stumbling points one might encounter when using (and) this way. Thanks for the feedback :)
pilrc?
I feel like I've seen the answer to this somewhere in the past when I was just a baby PicoLisper, but can't seem to find it now. Anyway, what's the canonical way to customize the default 'pil' environment? I'd like to have some of my own utilities and other goodies loaded when I start up. Can I just stick the necessary calls to (load) in .pilrc? :) Thanks!
RE: pilrc?
what's the canonical way to customize the default 'pil' environment? I'd like to have some of my own utilities and other goodies loaded when I start up. Can I just stick the necessary calls to (load) in .pilrc? :) I'm not aware of any .pilrc mechanics, search in mailing list also yields nothing, though such a mechanic might exist. I don't think this is the case. Have a look in your picolisp directory, within @bin/ there are the files 'picolisp' and 'pil. 'picolisp' is the actual binary generated by building picolisp. You usually start the picolisp repl by executing 'pil', watch it in a text editor and you can see it is actually a simple script using the #! mechanism to start the 'picolisp' binary, followed by loading a few files from @lib/. Those files are considered standard, globales and functions defined in those files is also mentioned in the official reference, opposite to other functionality hiding within the @lib/ directory. So the answer to your question is probably to just craft a customized variant of the pil file, e.g. leaving out @lib/db.l if you don't have any use for the whole database functionality. Of course you could also customize it in a way to load a .pilrc in your home folder, e.g. (let Rc (pack (sys HOME) /.pilrc) (when (info Rc) (load Rc) ) ) thought this might end in an error when .pilrc happens to exist but is a directory, so maybe you want to do: (let Rc (pack (sys HOME) /.pilrc) (when (num? (car (info Rc))) (load Rc) ) ) Regards, beneroth
Unnest your mess with 'and'
Hi list, I was thinking about some of the things brought up in the last thread, 'The `if-let` construct', notably Mike's comment about certain idioms being useless within the PicoLisp feature set. Now I like Clojure's '-' just as much as the next Clojure enthusiast, but I agree we don't need it in PicoLisp. I wrote a little tutorial explaining how we can use 'and' to accomplish the same thing as '-' and friends. It can be found here, https://github.com/erdg/learning-picolisp/blob/master/unnest-your-mess-with-and.md What do you all think of this technique? Any feedback would be great. I plan to add a bunch more mini-tutorials to this repo in the coming months to help those new to the language start to feel more at home. Cheers, Erik
