undefined | Better HN

0 pointsghostly_s18d ago0 comments

> A city can also exist in multiple zip codes. And there can be multiple cities with the same name in the same state.

These are reasons you cannot deduce the Zip from the city, not the opposite. A ZIP+4 actually encodes all other information for a US address.

0 comments

Someone123418d ago

Nobody knows their +4 code. You cannot ask for information 90%+ of people won't have.

fingerlocks18d ago

If asking for the zip first was more common then we quickly learn those four extra digits because the auto fill benefits would be immediately obvious

awesome_dude18d ago

Why?

I have a 4 digit postcode, I have to look it up every time I have to fill in an address form for delivery.

I've had people screw 1 digit up in that postcode and their items (a laptop in one case) went to the completely wrong city.

A code sounds foolproof, until you realise most people don't engage with them for most of their lives - you don't tell the uber driver the zip/post code you are waiting in, and travelling to, nobody does.

edit: just to add - Magic numbers are bad. Software engineers know that a number that's undocumented in code is unmaintainable, a zip code is worse.

2 more replies

tokyobreakfast18d ago

Of course they do.

Let me uh just grab my utility bill...

PaulDavisThe1st18d ago

10% of the US population is 35 million people. That's a pretty weird version of "nobody".

collingreen18d ago

This is a bad hill to die on for a ux conversation. "10% can feel kind a big number when 100% is huge" is a funny argument, as is trying to be pedantic about "nobody knows" as a shortcut for "most people won't know and you can't rely on any particular user knowing". If 10% is big enough to matter I can't wait to tell you about 90%!

2 more replies

bombcar18d ago

A ZIP+4 does not encode all information.

Proof: a post office has its own zip code, for PO Boxes.

The +4 is the last four digits of the post office box.

If the Post Office has more than 10,000 boxes, the +4 will be duplicated.

twodave18d ago

Yeah, anyone who has had to work with USPS bar codes should know that internally these are called routing codes, and they come in 5, 9 and even 11 digit variants. The 11-digit one narrows down to a specific delivery point, but even that isn’t enough to derive an address (just enough to know whether you’re looking at the right one or not). Zip+4 codes also change frequently because they aren’t based on locations but on delivery routes and sequencing.

fn-mote18d ago

> Zip+4 codes also change frequently because they aren’t based on locations but on delivery routes and sequencing.

This was news for me. I know the few zip+4 I memorize never change.

I think the source for the parent is AI slop. See [1].

> Due to an increase in population or to the improve postal operations, the US Postal Service® will occasionally add a new ZIP Code or change ZIP Code boundaries.

The plus four digits encode:

> [67] : Sector or Several Blocks

> [89] : Segment or One Side of a Street

Note that this contradicts the parent.

[1]: https://faq.usps.com/s/article/ZIP-Code-The-Basics

1 more reply

Twey18d ago

ZIP+4? I think that's literally enough digits to give every house in the US (about 150,000,000 apparently) its own identifier.

collingreen18d ago

Zip isn't uniformly distributed numbers though so you dont have the equivalent of that many digits of decimal numbers. Other comments have more detail but just for the top level example the first number is the zone and goes from 0 on the east coast to 9 on the west.

bombcar18d ago

Only if there's never more than 10,000 addresses in a single zip code, which means that if you enforce that, you can force a zip code to appear by building enough house

Twey17d ago

I think my point is that if you're going to make people learn a 9-digit identifier for their house you might as well make that identifier unique and then that's the only information they need to fill in. Having non-unique 9-digit identifiers feels wasteful.

axiolite18d ago

That happens, and worse. I've lived in multiple areas that have had their zip code changed. Area codes, too, sometime more than once.

kube-system18d ago

There are far more addresses than there are houses

tokyobreakfast18d ago

Wrong. There can also be multiple cities in the same ZIP code. There is not a 1:1 relationship with a 5-digit ZIP as everyone is assuming here.

j / k navigate · click thread line to collapse

0 comments

Someone123418d ago

Nobody knows their +4 code. You cannot ask for information 90%+ of people won't have.

fingerlocks18d ago

If asking for the zip first was more common then we quickly learn those four extra digits because the auto fill benefits would be immediately obvious

awesome_dude18d ago

Why?

I have a 4 digit postcode, I have to look it up every time I have to fill in an address form for delivery.

I've had people screw 1 digit up in that postcode and their items (a laptop in one case) went to the completely wrong city.

edit: just to add - Magic numbers are bad. Software engineers know that a number that's undocumented in code is unmaintainable, a zip code is worse.

2 more replies

tokyobreakfast18d ago

Of course they do.

Let me uh just grab my utility bill...

PaulDavisThe1st18d ago

10% of the US population is 35 million people. That's a pretty weird version of "nobody".

collingreen18d ago

2 more replies

bombcar18d ago

A ZIP+4 does not encode all information.

Proof: a post office has its own zip code, for PO Boxes.

The +4 is the last four digits of the post office box.

If the Post Office has more than 10,000 boxes, the +4 will be duplicated.

twodave18d ago

fn-mote18d ago

> Zip+4 codes also change frequently because they aren’t based on locations but on delivery routes and sequencing.

This was news for me. I know the few zip+4 I memorize never change.

I think the source for the parent is AI slop. See [1].

> Due to an increase in population or to the improve postal operations, the US Postal Service® will occasionally add a new ZIP Code or change ZIP Code boundaries.

The plus four digits encode:

> [67] : Sector or Several Blocks

> [89] : Segment or One Side of a Street

Note that this contradicts the parent.

[1]: https://faq.usps.com/s/article/ZIP-Code-The-Basics

1 more reply

Twey18d ago

ZIP+4? I think that's literally enough digits to give every house in the US (about 150,000,000 apparently) its own identifier.

collingreen18d ago

bombcar18d ago

Only if there's never more than 10,000 addresses in a single zip code, which means that if you enforce that, you can force a zip code to appear by building enough house

Twey17d ago

axiolite18d ago

That happens, and worse. I've lived in multiple areas that have had their zip code changed. Area codes, too, sometime more than once.

kube-system18d ago

There are far more addresses than there are houses

tokyobreakfast18d ago

Wrong. There can also be multiple cities in the same ZIP code. There is not a 1:1 relationship with a 5-digit ZIP as everyone is assuming here.

j / k navigate · click thread line to collapse