4 ms·

That’s easy, a valid email address is one that is well formed, conforming to the specification for email addresses. I know what you’re trying to get at, but th

by simonh 5y ago

That’s easy, a valid email address is one that is well formed, conforming to the specification for email addresses. I know what you’re trying to get at, but that’s just a category error. It’s a misuse of the term valid in this context. For example my mail archive contains many emails from valid addresses for which there happens to be no currently active mail box end point. They’re still valid data though. The fact that people sometimes use th s term valid to mean something completely different is just an unfortunate linguistic accident, but its a mistake to think it’s meaningful.

still_grokking 5y ago
> conforming to the specification for email addresses You mean something that roughly matches this obvious regex: \A(?:[a-z0-9!#$%&'*+/=?^_‘{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_‘{|}~-]+)* | "(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f] | \\[\x01-\x09\x0b\x0c\x0e-\x7f])*") @ (?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])? | \[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3} (?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]: (?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f] | \\[\x01-\x09\x0b\x0c\x0e-\x7f])+) \])\z [ Source: https://www.regular-expressions.info/email.html https://www.regular-expressions.info/email.html ] That somehow doesn't look "easy" on my eyes. I'm not sure the parent's comment was serous.
- Risord 5y ago
  Thats propably because you are looking inlined assembly of definition. If you name and reuse all the partial patterns it become much more clear. Though regex is cool obfuscation method.
  - still_grokking 5y ago
    It would be than at least 3/4 of a page long I guess. The fun part is this is not even the full truth. As the list of TLD isn't very static any more it's additionally difficult to determine whether a host name is valid. That is only possible with some dynamic list (or a regex that would grow indefinitely and ever change). The presented solution doesn't even take this into account. The source page I've linked is a quite interesting read on that whole topic.
    - Risord 5y ago
      You propably would want to reuse referenced definitions like domain and IP which are not email specific. But yes all of our JS could be much shorter if we used APL but most of us like readability :P I kind of not get why TLD should be validated. Does it matter anymore than if sub domain is not registered of if IP is not reachable. I think valid as potentially deliverable and actually deliverable should be distincted (like well formed XML and schema validated XML).
      - still_grokking 5y ago
        The TLD part matters as some part of the email format is defined through the format of a valid host name. "something.com" is a valid host name, but "something.something" isn't currently a valid host name. So an email address "something@something.something" isn't a valid email address (currently). But at the end of the day this is all moot, imho. The "only" sane test to check the validity of an email address when someone shows you one is whether you can successfully deliver mail there. Because even an address is formally valid doesn't mean it will get accepted by all systems on it's way. Almost nobody follows the under specified, confusing, and contradictory specs to the letter. That was my point in the first place: Trying to validate email addresses is a rabbit hole. It's for sure everything, but not "simple", as claimed above.
        scns 5y ago
        OT but i like your username.
        simonh 5y ago
        The point I was making is that whether or not you can successfully deliver email is not a sensible test of the validity of an email address, looking at the address purely as data. As I pointed out, my email archive contains many email addresses that are no longer ‘valid’ by your definition, but they are still valid as data. By your definition email address validity changes literally on a moment to moment basis. Addresses are becoming invalid constantly and new ones are becoming valid constantly. It’s not a useful definition of validity, and not even something you can test meaningfully.
taeric 5y ago
Why is that valid? You already introduced a new term for this concept, well formed. Amusingly, this distinction constantly annoys me with contact managers. I don't want to change my friend's phone number to the new one. I want to mark the old one as no longer active, and add the new one. Similar for deceased family. Back to the point, you seem to want null punning for the empty string. But you still need to check for validity of the value when it is not empty. What does that really gain you?

by simonh 5y ago

still_grokking 5y ago

> conforming to the specification for email addresses You mean something that roughly matches this obvious regex: \A(?:[a-z0-9!#$%&'*+/=?^_‘{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_‘{|}~-]+)* | "(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f] | \\[\x01-\x09\x0b\x0c\x0e-\x7f])*") @ (?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])? | \[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3} (?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]: (?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f] | \\[\x01-\x09\x0b\x0c\x0e-\x7f])+) \])\z [ Source: https://www.regular-expressions.info/email.html https://www.regular-expressions.info/email.html ] That somehow doesn't look "easy" on my eyes. I'm not sure the parent's comment was serous.

Risord 5y ago
Thats propably because you are looking inlined assembly of definition. If you name and reuse all the partial patterns it become much more clear. Though regex is cool obfuscation method.
- still_grokking 5y ago
  It would be than at least 3/4 of a page long I guess. The fun part is this is not even the full truth. As the list of TLD isn't very static any more it's additionally difficult to determine whether a host name is valid. That is only possible with some dynamic list (or a regex that would grow indefinitely and ever change). The presented solution doesn't even take this into account. The source page I've linked is a quite interesting read on that whole topic.
  - Risord 5y ago
    You propably would want to reuse referenced definitions like domain and IP which are not email specific. But yes all of our JS could be much shorter if we used APL but most of us like readability :P I kind of not get why TLD should be validated. Does it matter anymore than if sub domain is not registered of if IP is not reachable. I think valid as potentially deliverable and actually deliverable should be distincted (like well formed XML and schema validated XML).
    - still_grokking 5y ago
      The TLD part matters as some part of the email format is defined through the format of a valid host name. "something.com" is a valid host name, but "something.something" isn't currently a valid host name. So an email address "something@something.something" isn't a valid email address (currently). But at the end of the day this is all moot, imho. The "only" sane test to check the validity of an email address when someone shows you one is whether you can successfully deliver mail there. Because even an address is formally valid doesn't mean it will get accepted by all systems on it's way. Almost nobody follows the under specified, confusing, and contradictory specs to the letter. That was my point in the first place: Trying to validate email addresses is a rabbit hole. It's for sure everything, but not "simple", as claimed above.
      - scns 5y ago
        OT but i like your username.
      - simonh 5y ago
        The point I was making is that whether or not you can successfully deliver email is not a sensible test of the validity of an email address, looking at the address purely as data. As I pointed out, my email archive contains many email addresses that are no longer ‘valid’ by your definition, but they are still valid as data. By your definition email address validity changes literally on a moment to moment basis. Addresses are becoming invalid constantly and new ones are becoming valid constantly. It’s not a useful definition of validity, and not even something you can test meaningfully.

taeric 5y ago

Why is that valid? You already introduced a new term for this concept, well formed. Amusingly, this distinction constantly annoys me with contact managers. I don't want to change my friend's phone number to the new one. I want to mark the old one as no longer active, and add the new one. Similar for deceased family. Back to the point, you seem to want null punning for the empty string. But you still need to check for validity of the value when it is not empty. What does that really gain you?