Next draft

_posts/2018-06-19-dateutil-parser-to-rust.md

@@ -21,29 +21,37 @@ what to do with your life (but you should totally keep reading).
 OK, fine, I guess I should start with *why* someone would do this.
 
 [Dateutil](https://github.com/dateutil/dateutil) is a Python library for handling dates.
-While the standard library support for time in Python is kinda dope, there's a lot of pieces
+The standard library support for time in Python is kinda dope, but there are a lot of extras
 that go into making it useful beyond just the [datetime](https://docs.python.org/3.6/library/datetime.html)
-module.
+module. `dateutil.parser` specifically is code to take all the super-weird time formats people
+come up with and turn them into something actually useful.
 
-Specifically, `dateutil.parser` is code to take all the super-weird time formats people
-come up with and turn them into something actually useful. Just like [everything else](https://zachholman.com/talk/utc-is-enough-for-everyone-right)
-[involving](https://i.redd.it/syw7q6gc77f01.jpg) [computers](https://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time)
-and [time](https://infiniteundo.com/post/25509354022/more-falsehoods-programmers-believe-about-time),
+Date/time parsing, it turns out, is just like everything else(https://zachholman.com/talk/utc-is-enough-for-everyone-right)
+involving(https://i.redd.it/syw7q6gc77f01.jpg) [computers](https://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time)
+and [time](https://infiniteundo.com/post/25509354022/more-falsehoods-programmers-believe-about-time):
 it feels like it shouldn't be that difficult to do, until you try to do it,
-and you realize that people just suck and this is why can't we have nice things.
-But alas, we can still try and make contemporary art out of the rubble.
+and you realize that people suck and this is why [we can't we have nice things](https://zachholman.com/talk/utc-is-enough-for-everyone-right).
+But alas, we'll try and make contemporary art out of the rubble and give it a
+pretentious name like *Time*.
 
-What makes `dateutil.parser` great is that there's single super-important function: `parse(time_string)`.
+![A gravel mound](/assets/images/2018-06-25-gravel-mound.jpg)
+> [Time](https://www.goodfreephotos.com/united-states/montana/elkhorn/remains-of-the-mining-operation-elkhorn.jpg.php)
+
+What makes `dateutil.parser` great is that there's single function with a single argument that drives
+what programmers interact with: [`parse(timestr)`](https://github.com/dateutil/dateutil/blob/6dde5d6298cfb81a4c594a38439462799ed2aef2/dateutil/parser/_parser.py#L1258).
 It takes in the time as a string, and gives you back a reasonable "look, this is the best
 anyone can possibly do to make sense of your input" value. It doesn't expect much of you.
-Which is great. And now it's in Rust.
+
+[And now it's in Rust.](https://github.com/bspeice/dtparse/blob/7d565d3a78876dbebd9711c9720364fe9eba7915/src/lib.rs#L1332)
 
 # Lost in Translation
 
-Having worked at Bank of America and seeing Java programmers try to be Python programmers,
-I'm admittedly hesitant to publish Python code that's pretending to be Rust.
+Having worked at a bulge-bracket bank watching Java programmers try to be Python programmers,
+I'm admittedly hesitant to publish Python code that's trying to be Rust.
 Interestingly, Rust code can actually do a great job of mimicking Python.
-It's certainly not idiomatic Rust, but [the Iterator pattern is the same](https://webcache.googleusercontent.com/search?q=cache:wkYMpktJtnUJ:https://jackstouffer.com/blog/porting_dateutil.html+&cd=3&hl=en&ct=clnk&gl=us).
+It's certainly not idiomatic Rust, but I've had better experiences
+than [this guy](https://webcache.googleusercontent.com/search?q=cache:wkYMpktJtnUJ:https://jackstouffer.com/blog/porting_dateutil.html+&cd=3&hl=en&ct=clnk&gl=us)
+who attempted the same thing for D. These are the actual take-aways:
 
 When transcribing code, **stay as close to the original library as possible**. I'm talking
 about using the same variable names, same access patterns, the whole shebang.
@@ -67,7 +75,7 @@ And while `dateutil` is pretty well-behaved about not skipping multiple stack fr
 take a while to verify.
 
 As another Python quirk, **be very careful about [long nested if-elif-else blocks](https://github.com/dateutil/dateutil/blob/16561fc99361979e88cccbd135393b06b1af7e90/dateutil/parser/_parser.py#L494-L568)**.
-I used to think that [Python's whitespace](https://www.xkcd.com/353/) was just there
+I used to think that Python's whitespace was just there
 to get you to format your code correctly. I think that no longer. It's way too easy
 to close an extra block and have incredibly weird issues in the logic.
 
@@ -82,8 +90,9 @@ Finally, **I really miss list comprehensions and dictionary comprehensions.**
 As a quick comparison, see 
 [this dateutil code](https://github.com/dateutil/dateutil/blob/16561fc99361979e88cccbd135393b06b1af7e90/dateutil/parser/_parser.py#L476)
 and [the implementation in Rust](https://github.com/bspeice/dtparse/blob/7d565d3a78876dbebd9711c9720364fe9eba7915/src/lib.rs#L619-L629).
-Ultimately, I hope that these can be added through macros, but I have a feeling that they'd actually
-need to be syntax extensions. Either way, they're expressive, save typing, and super-readable. Let's get more of that.
+I probably wrote it wrong, and I'm sorry. Ultimately, I hope that these comprehensions can be added through macros,
+but I have a feeling that they'd actually need to be syntax extensions. Either way, they're expressive, save typing,
+and are super-readable. Let's get more of that.
 
 # Using a young language
 
@@ -91,11 +100,10 @@ Now, Rust is exciting and new, which means that there's opportunity to make a su
 On more than one occasion I've had issues navigating the Rust ecosystem though.
 
 What I'll call the "canonical library" is still being built. In Python, if you need datetime parsing,
-you use `dateutil`. If you want [Decimal](https://docs.python.org/3.6/library/decimal.html) types,
-it's already in the standard library. It's probably
-[not strictly necessary in `dateutil`](https://github.com/dateutil/dateutil/blob/16561fc99361979e88cccbd135393b06b1af7e90/dateutil/parser/_parser.py#L1242),
-but I wanted to follow the principle of **stay as close to the original library as possible**
-and thus began my quest to find a decimal library in Rust. What I quickly found was summarized
+you use `dateutil`. If you want `decimal` types, it's already in the
+[standard library](https://docs.python.org/3.6/library/decimal.html). The way `dateutil` uses decimals
+probably isn't strictly necessary, but I wanted to follow the principle of **stay as close to the original library as possible**.
+Thus began my quest to find a decimal library in Rust. What I quickly found was summarized
 in a comment:
 
 > Writing a BigDecimal is easy. Writing a *good* BigDecimal is hard.
@@ -105,15 +113,14 @@ in a comment:
 In practice, this means that there are at least [4](https://crates.io/crates/bigdecimal)
 [different](https://crates.io/crates/rust_decimal) [implementations](https://crates.io/crates/decimal)
 [available](https://crates.io/crates/decimate). And that's a lot of decisions to worry about
-when all I'm thinking about is "I just want a reasonable Decimal library" and I'm forced to dig through a
-[couple](https://github.com/rust-lang/rust/issues/8937#issuecomment-31661916)
-[different](https://github.com/rust-lang/rfcs/issues/334)
-[threads](https://github.com/rust-num/num/issues/8) to figure out if the library I'm look at is DOA stable.
+when all I'm thinking about is "why can't [calendar reform](https://en.wikipedia.org/wiki/Calendar_reform) be a thing"
+and I'm forced to dig through a [couple](https://github.com/rust-lang/rust/issues/8937#issuecomment-31661916)
+[different](https://github.com/rust-lang/rfcs/issues/334) [threads](https://github.com/rust-num/num/issues/8)
+to figure out if the library I'm look at is dead or just stable.
 
-And even when the "canonical library" exists for something like timezones ([`pytz`](https://pythonhosted.org/pytz/) and
-more recently [`dateutil.tz`](https://dateutil.readthedocs.io/en/stable/tz.html) in Python), there's no guarantees
-that it will be well-maintained. [Chrono](https://github.com/chronotope/chrono) is currently the canonical datetime
-library in Rust, and just released version 0.4.3 like a week ago. Meanwhile, [chrono-tz](https://github.com/chronotope/chrono-tz)
+And even when the "canonical library" exists, there's no guarantees that it will be well-maintained.
+[Chrono](https://github.com/chronotope/chrono) is the *de facto* date/time library in Rust,
+and just released version 0.4.3 like a week ago. Meanwhile, [chrono-tz](https://github.com/chronotope/chrono-tz)
 appears to be dead in the water even though [there are people happy to help maintain it](https://github.com/chronotope/chrono-tz/issues/19).
 I know relatively little about it, but it appears that most of the release process is automated; keeping
 that up to date should be a no-brainer.
@@ -134,21 +141,20 @@ then first congratulations on sustaining human life, and second I don't mind kee
 I just want to try and balance keeping things moving with giving people the necessary time.
 
 I should also note that I'm still getting some best practices in place - CONTRIBUTING and CONTRIBUTORS files
-need to be added, as well as issue/PR templates. In progress.
+need to be added, as well as issue/PR templates. In progress. None of us are perfect.
 
 # Roadmap and Conclusion
 
 So if I've now built a `dateutil`-compatible parser, we're done, right? Of course not! That's not
 nearly ambitious enough.
 
-Ultimately, I'd love to have a library that's capable of essentially everything the Linux `date`
-command can do (and not `date` on OSX, because seriously, it's the worst). I know Rust has a
-coreutils rewrite going on, and this would be potentially an interesting candidate since it
-doesn't bring in a lot of extra dependencies for the functionality it provides.
-[`humantime`](https://crates.io/crates/humantime) also is able to parse durations,
-so maybe we negotiate something to integrate it all together?
+Ultimately, I'd love to have a library that's capable of parsing essentially everything the Linux `date`
+command can do (and not `date` on OSX, because seriously, BSD coreutils are the worst). I know Rust has a
+coreutils rewrite going on, and `dtparse` would be potentially an interesting candidate since it
+doesn't bring in a lot of extra dependencies. [`humantime`](https://crates.io/crates/humantime)
+could help pick up some of the (current) slack in dtparse, so maybe we can share and care with each other?
 
-All in all, I'm really hoping that nobody's already done this and I've spent a bit over a month
-on redundant code. So if it exists, tell me because I need to know, but be nice about it.
+All in all, I'm mostly hoping that nobody's already done this and I've spent a bit over a month
+on redundant code. So if it exists, tell me. I need to know, but be nice about it because I'm going to take it hard.
 
 And in the mean time, I'm looking forward to building more. Onwards.