… kind of.
Declarative has its advantages which are hyped all over the internet so I’ll skip that part. The painful downside of declarative approach is often the expressivity. Sample proofs:
Now you can have Python embedded in your CloudFormation file. That is part of the CloudFormation Macros which were introduced on 2018-09-06.
Happy coding, everyone!
I’m curious about programming languages. Not because I’m creating one right now. I always was. This post is about ideas and features that I have seen in Perl 6 and found interesting. If you are curious about programming languages in general, you should take a look at these.
There are various reasons for not stealing the interesting ideas from Perl 6:
- I’m trying to keep number of concepts in NGS as small as possible. If I’m not seeing huge immediate value in a concept – I skip it.
- Not taking anything that I think can confuse me or other programmers. I’m not talking here because someone is a beginner. I’m talking about confusing concepts.
- Simply because I don’t have enough resources to implement it at the moment.
Here are the interesting Perl 6 features, in no particular order (except the first one). There are also my comments whether I would like the feature in NGS or why not.
- Syntax. Very expressive an terse. Perl6 has even more of it than Perl 5. Now that we got rid of the
$ and friends in the room:
- Grammars. Would actually be nice to have something like that in NGS.
- Lots of operators. The most interesting concept is Metaoperators. I’m trying to keep the amount of syntax elements in NGS relatively low. There are already two syntaxes in NGS: commands and expressions. Not taking more syntax without serious need.
- How the “pointy block” syntax mixes with “for” syntax:
for @list -> @element . NGS already has several syntaxes for Lambdas.
- Flow control
- “when” flow control. The closest NGS has is “cond” and friends, stolen from Lisp.
- repeat while / repeat until . It would be nice to have something like that in NGS.
- once . Not sure about this one. The functionality might be needed.
- Slips. The behaviour is frightening me: if it does expand, how do I pass a Slip if I just want to pass it, say as an item of an array? NGS uses syntax for slips:
[1, 2, *myitems, 3, 4] which I think is cleaner. You know you can’t pass it because it’s syntax.
- .WHAT method. I stole something similar from Ruby: the
As a special note, I have seen a welcome change from
@arr . I think it removes confusion. (That was Perl 5 vs Perl 6).
Please don’t be offended if you are a Perl 6 hacker and you see that there is amazing feature that I have not mentioned. It could be that I’ve seen this in several other languages already or maybe I did not find it interesting or … maybe I just missed it. Don’t hesitate to leave a comment anyway.
Happy coding, in whatever language rocks your boat! Except for bash. Coding in bash will never be happy.
jq is a great tool. It does what bash can not – work with structured data. I use it. I would like not to use it.
In my opinion, working with structured data is such a basic thing that it makes much more sense to be handled by the language itself. I want my shell to be capable and I strongly disagree with the view that a shell “is not supposed to do that”. Shell is supposed to do whatever is needed to make my life easier. Handling structured data is one of these things.
If “shell is not supposed to do that”, by that logic, bash is not supposed to do anything except for running external commands and routing the data between them. Doesn’t it seem odd that bash does have builtin string manipulation then? Maybe bash shouldn’t have added associative arrays in version 4? … or arrays in version 2? How about
while ? Maybe bash shouldn’t have them either?
jq is a symptom that bash can’t handle today’s reality: structured data. The world is increasingly more about APIs. APIs consume and return structured data. I do work with APIs from shell. Don’t you guys use AWS CLI or any other API that returns JSON?
The reality has changed. bash hasn’t. I’m working on bash alternative. Please help me with it. Or at least spread the word.
If you don’t like my project, join Elvish . Elvish is another shell that supports structured data.
Happy coding! Hope it’s not in bash.
I bet you’ve seen a lot of scripts with seemingly innocent
if [ -e blah ];then ...; else ...; fi or something similar . What’s the problem?
if has at most two branches while
[[ have three different exit codes. Oops.
If you make a syntax error (or any other error occurs) in the
[[ expression, it will return the exit code 2 (or above, according to
if will take the
else branch. If you are lucky, you will notice the error message from the
[[ commands. If not, the
else branch will always be executed.
I don’t want to use bash. The pitfall above is one of the many reasons. Unfortunately, I do use bash because it’s still best tool for some tasks. I’m working on alternative to bash. It’s called NGS, the Next Generation Shell. In NGS, the situation above is solved as one would expect from a modern programming language: exit codes 2 and above throw exception.
If you also think that there should be a viable alternative to bash, you are welcome to help me working on it.
Happy coding! Hope it’s not in bash 🙂
I’ve got “protection” feature by default (and I didn’t notice I even had it up until now) from my internet provider, Bezeq International. In the last few days I was experiencing selective reachability. Some IPs were just blocked by the “protection”.
More than 20 minutes with support that wanted to install their binaries on my laptop (I couldn’t do it for many reasons) and then about 5 minutes with some more senior guy that after hearing the symptoms just turned that thing off. Everything works fine now.
Hope this helps other people so they could recognize the situation and immediately know what’s happening.
- One of GitHub web IPs was blocked.
- Broken FaceBook
;; ANSWER SECTION:
static.xx.fbcdn.net. 3599 IN CNAME scontent.xx.fbcdn.net.
scontent.xx.fbcdn.net. 59 IN A 184.108.40.206
- Broken AWS. Manifested in timeouts talking to various services endpoints.
Following are just screenshots of http://ec2-reachability.amazonaws.com/ :
I was hoping that smart guys vs bad situation will have another outcome but Terraform language for version 0.12 looks bad… as languages of Puppet and Ansible.
I’m not saying that people that made Puppet and Ansible are not smart. It’s that we could learn from the mistakes they made… unless we don’t consider those being mistakes.
Puppet and Ansible went through very similar difficult situation. They have limited themselves to a declarative format and then they tried to accommodate the real life. Terraform has this situation right now.
The situation is:
- Declarative format being used
- People need something more powerful, like a programming language because … real life where conditionals, loops and data transformations make much more sense than working around declarative languages limitations.
Interestingly enough, they all did not switch to a proper programming language. Maybe because that would be at least partially admitting that the product should have been a library in the first place?
Terraform is actually in very crappy situation because even if they decide to expose everything as a library as the main interface, I don’t see people start using Go for “infrastructure as code”. Not as smooth as Ruby or Python anyway.
Happy coding, everyone!
On a bit more positive note, the new splat operator looks like an improvement.
Terraform looks even more like a “normal” language with Conditional Operator Improvements and
null value. The conditional operator fixes previous oddities that it had.
Terraform got type system. Looks powerful. Just need to see that Terraform does not evolve to Scala 🙂
New template syntax brings more raw power. Looks good.
- HCL to JSON one-to-one mapping. When I read “having a clean 1:1 mapping between HCL and JSON, and ensuring every feature of HCL is supported in JSON” I immediately thought that there must be converting tools then… and was not disappointed 🙂 “In future versions of Terraform, we will also support native tooling to convert HCL to JSON and JSON to HCL cleanly (including comments)”
- “Comments in JSON” – nice!
Declarative languages failure
Approach that in my eyes failed, again and again, is to start with your own declarative language and then with time grow the language. (SQL being among notable exceptions)
Puppet is the best example. map and each, added in Puppet 4.0.0 are, in my opinion, just two in a sea of evidence that the envisioned simple format has failed to handle the needs of the real world.
Ansible’s loop looks bad as the whole idea of making top levels of programs in YAML based syntax (and the rest in Python).
In my opinion, it makes more sense to create a language first and then libraries for it, not a library and then a language around it.
My hope for Terraform
I think Terraform guys are smart. Among other things, it manifests in implementing data sources. Data sources make Terraform much more flexible. I think it’s very clever.
Terraform, which started declarative, are now inventing their own programming language. They are going the way of Puppet and Ansible. I hope they can do better, in this awkward situation: there are quite a lot of constraints on the programming language because of the existing syntax and semantics.
Happy coding, everyone!