5 ms·

Ansible is a Lisp?

52 points by soopurman 2y ago

axblount 2y ago
Not everything that can be represented with s-expressions is a lisp. For example: (html (body (h1 "Hello, World!"))) This does not mean that HTML is a lisp.
- anthk 2y ago
 Well: This webserver in Maclisp http://up.dfupdate.se/httpd%20html http://up.dfupdate.se/httpd%20html gave birth to this: http://up.dfupdate.se/ulml.html http://up.dfupdate.se/ulml.html
- anthk 2y ago
 Also, more than Lisp, clips would be a really good choice there. Defining constraints to configure a system? That's basically what literally Clips does. https://www.clipsrules.net/ https://www.clipsrules.net/
- cess11 2y ago
 OK, but what about the homoiconicity and syntax macros?
 - axblount 2y ago
 I don't know Ansible well enough to say for sure, but the macro example seems like more of a C preprocessor style "macro." I don't see how it's doing anything more than filling in a template.
 - cess11 2y ago
 It's executed at runtime, not before some compilation stage.
 - simplify 2y ago
 "What is homoiconicity then? Typical definitions state that it is simply “code as data”, will point to a relationship between a program’s structure and syntax or note that the program source is expressed in a primitive data-type of the language. In the below, we will show that none of these definitions make much sense." https://www.expressionsofchange.org/dont-say-homoiconic/ https://www.expressionsofchange.org/dont-say-homoiconic/
 - cess11 2y ago
 In this context it seems to refer to programming in a language where the developer facing code is represented in terms of data structure literals within the language. It's a reasonable understanding of what is usually meant in a Lisp-like setting. The code is a list, so you can trivially construct and deconstruct executable lists, just like you can trivially construct data carrying lists. One could make clever quips that this isn't enough, you need quote/unquote as well to make it practical, and is that really implied by homoiconicity? Should we really use this word? Maybe we should pay someone to make up a new one?
- mepian 2y ago
 I agree, recently I shared here a great article by Hayley Patton on this exact topic: https://gist.github.com/no-defun-allowed/4f0a06e17b3ce74c6aeac514281f350f https://gist.github.com/no-defun-allowed/4f0a06e17b3ce74c6ae...
- saghm 2y ago
 You'd think this would be more understood given that pretty much the whole point of lisp is to be pretty close to just representing an AST without relatively few frills. The idea that we can represent most languages with a tree-like structure isn't particularly novel.
- jimbokun 2y ago
 But that can be perfectly valid Lisp. Lisp libraries producing HTML often look just like that.
- btilly 2y ago
 Not all of HTML can be represented with s-expressions. The following is perfectly valid. Hello World! Greetings Earthlings!
 - MathMonkeyMan 2y ago
 I never noticed that, though "doesn't require a closing tag" and "requires that there is no closing tag" ought to have been hints for me.
 - LegionMammal978 2y ago
 And yet it's semantically identical to Hello World!</> Greetings Earthlings! You can see this by looking at the innerHTML, which is really just a serialized form of the DOM tree.
 - ptx 2y ago
 Is it actually valid? W3C's HTML validator complains about invalid nesting. It might work because the HTML5 parsing algorithm produces well-defined results for broken HTML, but I'm not sure that's the same as "perfectly valid" – the spec calls such markup "misnested" and "erroneous" [0]. [0] https://html.spec.whatwg.org/#an-introduction-to-error-handling-and-strange-cases-in-the-parser https://html.spec.whatwg.org/#an-introduction-to-error-handl...
 - btilly 2y ago
 It certainly was valid according to the original specs. I first saw it as an example over 20 years ago in a debate about whether XHTML should replace HTML 4.0.
Attummm 2y ago
This is quite a stretch to call Ansible, which consists of YAML files with syntactic sugar and some light Python evaluation, 'Lisp'. I thought reading the article would make less inflammatory but it didn't.
- baq 2y ago
  Yeah I agree, Ansible would be so much better if it was Lisp-first with a perfectly non-scary I'm-a-devops YAML syntax instead of OMG-parens-nobody-understands-Lisp Lisp syntax.
  - eternityforest 2y ago
    I'm guessing you'd probably break the declarativeness if you exposed the full power of LISP, but limited subsets in YAML work pretty well. I especially like how well suited it is to visual block based editing. Blockly and Node Red let you put stuff anywhere in 2D space, a satisfying auto formatter isn't really possible, and traditional flow charts can easily get big and messy. But if you look at DRAKON, their charts pretty much always look nice. And looking at ladder logic, It's almost but not quite a set of 1D flow charts. If you strip it down more, events that trigger a list of commands until a command returns False is a really simple model without much learning time, and it's very easy to create a visual editor Giving people the full power of LISP would probably result in people writing imperative programs rather than building up an ecosystem of declarative plugins though. And it seems that the consensus is it doesn't become a LISP just because you can implement it in nested lists....
- jimbokun 2y ago
  It’s a homoiconic language like Lisp, just with YAML instead of s-expressions.
  - fargle 2y ago
    that's beyond a real stretch - is XSLT a LISP then? simply using YAML (or json or any equivalent data/markup syntax as the basis for a DSL syntax does not make it homoiconic. in this case, the very rigid structure of playbooks and tasks, etc. within YAML is also part of the syntax. just the fact that you can generate arbitrary YAML (or json or etc.) from within a copy utility does not come close to homoiconicity of a LISP. can you effortlessly move back/forth from data to code? is everything both code and data at the same time? what's the Ansible equivalent to quasi-quote, for instance? is a bash script that sources (or creates or evals) a list of variable assignments in bash syntax homoiconic? due to eval, bash would seem a hell of a lot closer. and those really aren't "syntactic macros" either, unless you'd be happy to define an MS-DOS .bat file that generates and calls a .bat file fragment "syntactic macros". it's using an external file ffs. Ansible is good for what it does, but it has an extremely limited and rigid "flow-control" (if we can even call it that) and is more of a declarative language/config file than a general language. this represents a pretty naive superficial understanding of these LISP features. points for making us think though.
behnamoh 2y ago
Either the author doesn't know what Lisp means (the "essence" of Lisp), or just wants to stretch YAML to mean Lisp.
jeffrallen 2y ago
See also https://en.m.wikipedia.org/wiki/Greenspun%27s_tenth_rule https://en.m.wikipedia.org/wiki/Greenspun%27s_tenth_rule "Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp."
- anonzzzies 2y ago
  Yes, that’s what I think off when I see ansible, not that it actually is a lisp. It’s a poor hack for something you can trivially do with lisp since forever. Like most of these things and indeed Greenspuns rule says we will find that; you need the solution for something complicated so you start building something simple, add more features and end up with something you should’ve done in lisp from the start. And of course now you miss most (all) of the benefits.
- sunshine-o 2y ago
  Blame the poor computer science education of most people nowadays (could be self-taught or university). Discovering that code is data and data is code is discovering the moon. And inferring that your sad configuration management system based on an ugly data language is kind of related to Lisp must be mind blowing. Also bonus fact, XML is a lisp too ! Actually maybe we could have written ansible in lisp directly to save us the trouble.
- saghm 2y ago
  This quote has always seemed very strange to me. I feel like the implicit argument (that just using lisp instead of making a program that has more limited semantics that conform directly to the intended purpose) is not a great one. Obviously informally-specified, bug-ridden, and slow are not good things, but I'd argue those are also not specific to Fortran or C but just to any "sufficiently complicated program". People make a big deal about the Church-Turing thesis, but I think it gets taken too far sometimes because the important part of a programming language isn't always what's possible to do in the language but what _isn't_, and I'd argue most of the large improvements in languages over time are about that; not having undefined behavior, null-pointer errors, and runtime type errors are all huge improvements in programming productivity that only exist because we made languages that don't allow you to do certain things. At the end of the day, quite a lot of the work in programming boils down to ensuring that what you wrote does _exactly_ what you intend rather than behaving in some other way, and that means identifying and eliminating places where it diverges. There are a lot of common patterns for places where these issues occur, and a language that can identify those patterns and make it impossible for you to write a program that has those mistakes is saving you time up front.
mattmein 2y ago
Related: https://yamlscript.org/ https://yamlscript.org/
- baq 2y ago
  This is... beautiful.
- cess11 2y ago
  Seems weird enough to be fun, especially since it has recursion: https://rosettacode.org/wiki/Fibonacci_sequence#YAMLScript https://rosettacode.org/wiki/Fibonacci_sequence#YAMLScript
medo-bear 2y ago
My set of lego pieces is a Lisp
nathell 2y ago
Bash is a Lisp, too. https://blog.danieljanus.pl/2014/05/20/you-already-use-lisp-syntax/ https://blog.danieljanus.pl/2014/05/20/you-already-use-lisp-...
- ptx 2y ago
  Bash feels more like a C buffer overflow vulnerability than a Lisp: When you're not careful your data tends to leak across its boundaries and get mixed up with your code. Is there a way to quote data in Bash to safely insert it into a piece of code, the way you can in Lisp?
  - kazinator 2y ago
    In Bash, yes. Or, almost. The printf built-in command has a %q conversion specifier which quotes the argument such that the result can be used as input into the shell. Such a thing cannot be inserted into a quote without affecting its meaning, but what you can do is terminate the quote before and after it. 'stuff before'$(printf "%q" "$value")'stuff after' In this case, because it's a single quote, we need to terminate it anyway, order to activate the command substitution syntax.
James_K 2y ago
> YAML as executable code Why must we do these things to ourselves?
- Zambyte 2y ago
  I don't think my aversion is actually YAML. I have been playing around a lot with Benthos lately, and it is actually quite pleasant.
- Woshiwuja 2y ago
  YAML is one of the best configs languages imo. Using it as executable code? MEH
lanstin 2y ago
I thought this was going to be a python thing that exploited functions returning functions with their lexical scope. I find too many syntactical macros tends to encourage excessively dense code. Tho I usually use packer and terraform to configure my end VMs not ansible. A PR to either packer repo or territory repo and push the button to recreate the resources.
fiddlerwoaroof 2y ago
Actually, ansible is a prolog. I played around with marelle[1] a bit for managing my Mac configuration and I realized that the core of the typical configuration management tool just is a prolog: it gathers facts from the systems you have, compares them with a desired state you’ve specified declaratively and executes a plan to get from the current state to the specified one. Prolog does the planning more or less “for free” because of its evaluation model. [1]: https://github.com/larsyencken/marelle https://github.com/larsyencken/marelle
sgt 2y ago
Ansible is great, but using YAML still bugs me. Would just be a lot easier with HCL (Hashicorp) or something else.
- orwin 2y ago
  At my first job, we had a perl script to transform json into a yaml inventory file (it then allowed us to serve a form to clients that would act as a yaml, but i left a bit before the feature was implemented). We still had to write our module in yaml though. Still, the greybeard who come up with the initial design and architecture was the best dev i've ever worked with, to this day. I wasn't ready to learn as much as i ought to do, sadly.
vindarel 2y ago
Those are 2 lisp tools not unlike Ansible: * [Consfigurator](https://spwhitton.name/tech/code/consfigurator/ https://spwhitton.name/tech/code/consfigurator/) - Lisp declarative configuration management system. You can use it to configure hosts as root, deploy services as unprivileged users, build and deploy containers, and produce disc images. [GPL3][2]. * [cl-unix-cybernetics](https://github.com/cl-unix-cybernetics/cl-unix-cybernetics https://github.com/cl-unix-cybernetics/cl-unix-cybernetics) (previously Adams) - UNIX system administration in Common Lisp. Not unlike Ansible, Chef or Puppet. [ISC][22]. - You describe your systems (hosts) using resources having properties. The properties are then probed and synchronized using only /bin/sh on the remote host, and /usr/bin/ssh on the control host. (awesome-cl)

52 points by soopurman 2y ago

Not everything that can be represented with s-expressions is a lisp. For example: (html (body (h1 "Hello, World!"))) This does not mean that HTML is a lisp.

anthk 2y ago
Well: This webserver in Maclisp http://up.dfupdate.se/httpd%20html http://up.dfupdate.se/httpd%20html gave birth to this: http://up.dfupdate.se/ulml.html http://up.dfupdate.se/ulml.html
anthk 2y ago
Also, more than Lisp, clips would be a really good choice there. Defining constraints to configure a system? That's basically what literally Clips does. https://www.clipsrules.net/ https://www.clipsrules.net/
cess11 2y ago
OK, but what about the homoiconicity and syntax macros?
- axblount 2y ago
  I don't know Ansible well enough to say for sure, but the macro example seems like more of a C preprocessor style "macro." I don't see how it's doing anything more than filling in a template.
  - cess11 2y ago
    It's executed at runtime, not before some compilation stage.
- simplify 2y ago
  "What is homoiconicity then? Typical definitions state that it is simply “code as data”, will point to a relationship between a program’s structure and syntax or note that the program source is expressed in a primitive data-type of the language. In the below, we will show that none of these definitions make much sense." https://www.expressionsofchange.org/dont-say-homoiconic/ https://www.expressionsofchange.org/dont-say-homoiconic/
  - cess11 2y ago
    In this context it seems to refer to programming in a language where the developer facing code is represented in terms of data structure literals within the language. It's a reasonable understanding of what is usually meant in a Lisp-like setting. The code is a list, so you can trivially construct and deconstruct executable lists, just like you can trivially construct data carrying lists. One could make clever quips that this isn't enough, you need quote/unquote as well to make it practical, and is that really implied by homoiconicity? Should we really use this word? Maybe we should pay someone to make up a new one?
mepian 2y ago
I agree, recently I shared here a great article by Hayley Patton on this exact topic: https://gist.github.com/no-defun-allowed/4f0a06e17b3ce74c6aeac514281f350f https://gist.github.com/no-defun-allowed/4f0a06e17b3ce74c6ae...
saghm 2y ago
You'd think this would be more understood given that pretty much the whole point of lisp is to be pretty close to just representing an AST without relatively few frills. The idea that we can represent most languages with a tree-like structure isn't particularly novel.
jimbokun 2y ago
But that can be perfectly valid Lisp. Lisp libraries producing HTML often look just like that.
btilly 2y ago
Not all of HTML can be represented with s-expressions. The following is perfectly valid. Hello World! Greetings Earthlings!
- MathMonkeyMan 2y ago
 I never noticed that, though "doesn't require a closing tag" and "requires that there is no closing tag" ought to have been hints for me.
- LegionMammal978 2y ago
 And yet it's semantically identical to Hello World!</> Greetings Earthlings! You can see this by looking at the innerHTML, which is really just a serialized form of the DOM tree.
- ptx 2y ago
 Is it actually valid? W3C's HTML validator complains about invalid nesting. It might work because the HTML5 parsing algorithm produces well-defined results for broken HTML, but I'm not sure that's the same as "perfectly valid" – the spec calls such markup "misnested" and "erroneous" [0]. [0] https://html.spec.whatwg.org/#an-introduction-to-error-handling-and-strange-cases-in-the-parser https://html.spec.whatwg.org/#an-introduction-to-error-handl...
 - btilly 2y ago
 It certainly was valid according to the original specs. I first saw it as an example over 20 years ago in a debate about whether XHTML should replace HTML 4.0.

Attummm 2y ago

This is quite a stretch to call Ansible, which consists of YAML files with syntactic sugar and some light Python evaluation, 'Lisp'. I thought reading the article would make less inflammatory but it didn't.

baq 2y ago
Yeah I agree, Ansible would be so much better if it was Lisp-first with a perfectly non-scary I'm-a-devops YAML syntax instead of OMG-parens-nobody-understands-Lisp Lisp syntax.
- eternityforest 2y ago
  I'm guessing you'd probably break the declarativeness if you exposed the full power of LISP, but limited subsets in YAML work pretty well. I especially like how well suited it is to visual block based editing. Blockly and Node Red let you put stuff anywhere in 2D space, a satisfying auto formatter isn't really possible, and traditional flow charts can easily get big and messy. But if you look at DRAKON, their charts pretty much always look nice. And looking at ladder logic, It's almost but not quite a set of 1D flow charts. If you strip it down more, events that trigger a list of commands until a command returns False is a really simple model without much learning time, and it's very easy to create a visual editor Giving people the full power of LISP would probably result in people writing imperative programs rather than building up an ecosystem of declarative plugins though. And it seems that the consensus is it doesn't become a LISP just because you can implement it in nested lists....
jimbokun 2y ago
It’s a homoiconic language like Lisp, just with YAML instead of s-expressions.
- fargle 2y ago
  that's beyond a real stretch - is XSLT a LISP then? simply using YAML (or json or any equivalent data/markup syntax as the basis for a DSL syntax does not make it homoiconic. in this case, the very rigid structure of playbooks and tasks, etc. within YAML is also part of the syntax. just the fact that you can generate arbitrary YAML (or json or etc.) from within a copy utility does not come close to homoiconicity of a LISP. can you effortlessly move back/forth from data to code? is everything both code and data at the same time? what's the Ansible equivalent to quasi-quote, for instance? is a bash script that sources (or creates or evals) a list of variable assignments in bash syntax homoiconic? due to eval, bash would seem a hell of a lot closer. and those really aren't "syntactic macros" either, unless you'd be happy to define an MS-DOS .bat file that generates and calls a .bat file fragment "syntactic macros". it's using an external file ffs. Ansible is good for what it does, but it has an extremely limited and rigid "flow-control" (if we can even call it that) and is more of a declarative language/config file than a general language. this represents a pretty naive superficial understanding of these LISP features. points for making us think though.

behnamoh 2y ago

Either the author doesn't know what Lisp means (the "essence" of Lisp), or just wants to stretch YAML to mean Lisp.

jeffrallen 2y ago

See also https://en.m.wikipedia.org/wiki/Greenspun%27s_tenth_rule https://en.m.wikipedia.org/wiki/Greenspun%27s_tenth_rule "Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp."

anonzzzies 2y ago
Yes, that’s what I think off when I see ansible, not that it actually is a lisp. It’s a poor hack for something you can trivially do with lisp since forever. Like most of these things and indeed Greenspuns rule says we will find that; you need the solution for something complicated so you start building something simple, add more features and end up with something you should’ve done in lisp from the start. And of course now you miss most (all) of the benefits.
sunshine-o 2y ago
Blame the poor computer science education of most people nowadays (could be self-taught or university). Discovering that code is data and data is code is discovering the moon. And inferring that your sad configuration management system based on an ugly data language is kind of related to Lisp must be mind blowing. Also bonus fact, XML is a lisp too ! Actually maybe we could have written ansible in lisp directly to save us the trouble.
saghm 2y ago
This quote has always seemed very strange to me. I feel like the implicit argument (that just using lisp instead of making a program that has more limited semantics that conform directly to the intended purpose) is not a great one. Obviously informally-specified, bug-ridden, and slow are not good things, but I'd argue those are also not specific to Fortran or C but just to any "sufficiently complicated program". People make a big deal about the Church-Turing thesis, but I think it gets taken too far sometimes because the important part of a programming language isn't always what's possible to do in the language but what _isn't_, and I'd argue most of the large improvements in languages over time are about that; not having undefined behavior, null-pointer errors, and runtime type errors are all huge improvements in programming productivity that only exist because we made languages that don't allow you to do certain things. At the end of the day, quite a lot of the work in programming boils down to ensuring that what you wrote does _exactly_ what you intend rather than behaving in some other way, and that means identifying and eliminating places where it diverges. There are a lot of common patterns for places where these issues occur, and a language that can identify those patterns and make it impossible for you to write a program that has those mistakes is saving you time up front.

mattmein 2y ago

Related: https://yamlscript.org/ https://yamlscript.org/

baq 2y ago
This is... beautiful.
cess11 2y ago
Seems weird enough to be fun, especially since it has recursion: https://rosettacode.org/wiki/Fibonacci_sequence#YAMLScript https://rosettacode.org/wiki/Fibonacci_sequence#YAMLScript

medo-bear 2y ago

My set of lego pieces is a Lisp

nathell 2y ago

Bash is a Lisp, too. https://blog.danieljanus.pl/2014/05/20/you-already-use-lisp-syntax/ https://blog.danieljanus.pl/2014/05/20/you-already-use-lisp-...

ptx 2y ago
Bash feels more like a C buffer overflow vulnerability than a Lisp: When you're not careful your data tends to leak across its boundaries and get mixed up with your code. Is there a way to quote data in Bash to safely insert it into a piece of code, the way you can in Lisp?
- kazinator 2y ago
  In Bash, yes. Or, almost. The printf built-in command has a %q conversion specifier which quotes the argument such that the result can be used as input into the shell. Such a thing cannot be inserted into a quote without affecting its meaning, but what you can do is terminate the quote before and after it. 'stuff before'$(printf "%q" "$value")'stuff after' In this case, because it's a single quote, we need to terminate it anyway, order to activate the command substitution syntax.

James_K 2y ago

> YAML as executable code Why must we do these things to ourselves?

Zambyte 2y ago
I don't think my aversion is actually YAML. I have been playing around a lot with Benthos lately, and it is actually quite pleasant.
Woshiwuja 2y ago
YAML is one of the best configs languages imo. Using it as executable code? MEH

lanstin 2y ago

I thought this was going to be a python thing that exploited functions returning functions with their lexical scope. I find too many syntactical macros tends to encourage excessively dense code. Tho I usually use packer and terraform to configure my end VMs not ansible. A PR to either packer repo or territory repo and push the button to recreate the resources.

fiddlerwoaroof 2y ago

Actually, ansible is a prolog. I played around with marelle[1] a bit for managing my Mac configuration and I realized that the core of the typical configuration management tool just is a prolog: it gathers facts from the systems you have, compares them with a desired state you’ve specified declaratively and executes a plan to get from the current state to the specified one. Prolog does the planning more or less “for free” because of its evaluation model. [1]: https://github.com/larsyencken/marelle https://github.com/larsyencken/marelle

sgt 2y ago

Ansible is great, but using YAML still bugs me. Would just be a lot easier with HCL (Hashicorp) or something else.

orwin 2y ago
At my first job, we had a perl script to transform json into a yaml inventory file (it then allowed us to serve a form to clients that would act as a yaml, but i left a bit before the feature was implemented). We still had to write our module in yaml though. Still, the greybeard who come up with the initial design and architecture was the best dev i've ever worked with, to this day. I wasn't ready to learn as much as i ought to do, sadly.

vindarel 2y ago

Those are 2 lisp tools not unlike Ansible: * [Consfigurator](https://spwhitton.name/tech/code/consfigurator/ https://spwhitton.name/tech/code/consfigurator/) - Lisp declarative configuration management system. You can use it to configure hosts as root, deploy services as unprivileged users, build and deploy containers, and produce disc images. [GPL3][2]. * [cl-unix-cybernetics](https://github.com/cl-unix-cybernetics/cl-unix-cybernetics https://github.com/cl-unix-cybernetics/cl-unix-cybernetics) (previously Adams) - UNIX system administration in Common Lisp. Not unlike Ansible, Chef or Puppet. [ISC][22]. - You describe your systems (hosts) using resources having properties. The properties are then probed and synchronized using only /bin/sh on the remote host, and /usr/bin/ssh on the control host. (awesome-cl)