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A couple million lines of Haskell: Production engineering at Mercury

blog.haskell.org

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Re: A couple million lines of Haskell: Production engineering at Mercury

#21

Post by ipnon »

maz1b wrote: post #2

I think perhaps contrary to popular belief, Mercury choosing Haskell and their early leadership having such a storied experience in it probably played some non-insignificant role in their success. As a customer of Mercury, it's truly one of the critical companies my toolkit, and I just can't help but feel that their choosing of Haskell made their progress, development and overall journey that much better. I realize t…

I have noticed that everything in their app Just Works. It's very satisfying coming from other services!

Re: A couple million lines of Haskell: Production engineering at Mercury

#22

Post by miki123211 »

bri3d wrote: post #7

> Haskell gives you tools to encode these incantations in types so they cannot be forgotten. This is, for my money, the single most valuable thing the language offers a production engineering organization. Haskell is admittedly, probably the most powerful widely (or even somewhat widely) used language for doing this, but this general pattern works really well in Rust and TypeScript too and is one of my very favorite…

This isn't specific to Rust or Typescript. You can do this in basically any language.

Imagine you have to distinguish between unescaped and escaped strings for security purposes. Even with a dynamically typed language, you can keep escaped strings as an Escaped class, with escape(str)->Escaped and dangerouslyAssumeEscaped(str)->Escaped functions (or static methods). There's a performance cost to this, so that's a tradeoff you have to weigh, but it is possible.

Another way of doing this is Application Hungarian[1], though that relies on the programmer more than it does on the compiler.

[1] https://www.joelonsoftware.com/2005/05/11/making-wrong-code-...

Re: A couple million lines of Haskell: Production engineering at Mercury

#23

Post by mbac32768 »

threethirtytwo wrote: post #4

I really believe in FP and Haskell but I want to examine this objectively. Empirically speaking is what Mercury done successful truly because of Haskell? Do they have metrics that demonstrates clear superiority along some vectored trait like complexity, bug count, etc? >A couple million lines of Haskell, maintained by people who learned the language on the job, at a company that moves huge amounts of money? The conve…

The irony of these fancy FP languages that were designed to develop compilers or to get PL academics off is that they're actually also really good at the most mundane code imaginable.

Being able to minimize boilerplate and have strong refactoring and bug resistant types is a huge edge.

The only problem is their ecosystems are limited so you might spend more time than you like implementing an API or binding a system library.

Re: A couple million lines of Haskell: Production engineering at Mercury

#24

Post by [deleted] »

cmrdporcupine wrote: post #16
dnnddidiej wrote: post #3

I think you have to get a Haskell job early in career and stick to Haskell jobs. Breaking in is really hard as you come without experience there will be plenty of others with Haskell experience to compete. And because the jobs are rare if it doesnt work out (company becomes bad to work for or layoff) you can be unstuck (or I guess you would switch to Rust, Scala or F#)

My fear with something like Haskell particularly and with hiring people who really love Haskell is that you risk ending up with a certain kind of personality who fetishizes the tool over the problem. I've been this person, and I've worked with this kind of person, and been the victim of this kind of person. They love language X, or framework Y, and are convinced that so many problems in front of them are shaped in a…

[deleted]

Re: A couple million lines of Haskell: Production engineering at Mercury

#25

Post by golem14 »

I'm not particularly into Haskell or functional languages, but I came here to say it warms my heart to hear that people in finance actually embrace it (also J/APL). It seems like a good choice for banking.

The Mercury site also looks way better than most other banks I have ever used (load speed is also very good.) On the danger of seeming like a shill (I'm not), I'm tempted to try them out.

Re: A couple million lines of Haskell: Production engineering at Mercury

#26

Post by thot_experiment »

My bestie works at this company and looking from the outside they have a good engineering culture. I do think Haskell is the right tool for the job, and they are playing to it's strengths, but part of me wonders if a lot of their success is attributable to the place just being well run in general.

Re: A couple million lines of Haskell: Production engineering at Mercury

#27

Post by sillysaurusx »

golem14 wrote: post #25

I'm not particularly into Haskell or functional languages, but I came here to say it warms my heart to hear that people in finance actually embrace it (also J/APL). It seems like a good choice for banking. The Mercury site also looks way better than most other banks I have ever used (load speed is also very good.) On the danger of seeming like a shill (I'm not), I'm tempted to try them out.

Do it. You won’t be disappointed. I’ve been using them for about 5 years now.

Re: A couple million lines of Haskell: Production engineering at Mercury

#28

Post by ironmagma »

thot_experiment wrote: post #26

My bestie works at this company and looking from the outside they have a good engineering culture. I do think Haskell is the right tool for the job, and they are playing to it's strengths, but part of me wonders if a lot of their success is attributable to the place just being well run in general.

That would not run counter to the popular (whether true or not) idea that by using functional programming languages you filter for a higher quality labor pool / applicant pool.

Re: A couple million lines of Haskell: Production engineering at Mercury

#29

Post by jwsteigerwalt »

ipnon wrote: post #21
maz1b wrote: post #2

I think perhaps contrary to popular belief, Mercury choosing Haskell and their early leadership having such a storied experience in it probably played some non-insignificant role in their success. As a customer of Mercury, it's truly one of the critical companies my toolkit, and I just can't help but feel that their choosing of Haskell made their progress, development and overall journey that much better. I realize t…

I have noticed that everything in their app Just Works. It's very satisfying coming from other services!

I feel the same way. I only started using Mercury about 6 months ago and I’m continually impressed that it just makes sense.

Re: A couple million lines of Haskell: Production engineering at Mercury

#30

Post by sillysaurusx »

I just wanted to leave a glowing comment about Mercury itself, since this is one of the few times I’ll be able to.

I’ve been using Mercury for 5 years. In that time, I’ve been able to wire transfer money without having to worry it might disappear (functionally impossible at certain other banks), created hundreds of virtual debit cards each with their own limit and pulling from different accounts, created dozens of accounts (a “place to put money”) named by function (each of my household utilities gets its own account, with an automatic rule to pull in money whenever it gets paid out), and… well, I think that covers everything.

This has given me unprecedented insight into my financial life. I know exactly how much I spend on groceries, on each utility, and on entertainment. I can project ahead and get a burn rate for my household. And my ex wife uses it too, on the same login, which is as easy as “make an account named with her first name” and a corresponding virtual debit card.

I’m convinced the only reason people don’t use Mercury is that they don’t know what they’re missing.

You have to pay for personal banking (a couple hundred a year iirc), but the business banking is free. If you want to try them out, you can start an LLC for a few dollars (at least in Missouri) and get overnight access to Mercury. All that’s required is your EIN.

They’ve been one of the single best products I’ve ever used. The sole wrinkle was when they canceled all their existing virtual cards due to reasons, which threw my recurring billing into chaos. But every great company is allowed at least one mega annoyance, and that one was a blip.

If you’re wondering whether to try them out, the answer is yes, and I’m excited for you to discover how cool it is. https://www.mercury.com

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