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Implementing Regular Expressions in TypeScript Types (Badly)

skalt.github.io

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Re: Implementing Regular Expressions in TypeScript Types (Badly)

#2

Post by penguin359 »

Having compile-time RegEx's would certainly fix some issues I've had with them in Python. As they are just buried in plain strings, there's no validation of their syntax until you hit the line of code that tried to use them only to discover that Python 3.12 has changed the syntax and what was once working is now broken. I'd love to see this validated at compile-time/load-time of any language to avoid those unexpected surprises.

Re: Implementing Regular Expressions in TypeScript Types (Badly)

#3

Post by ygra »

penguin359 wrote: post #2

Having compile-time RegEx's would certainly fix some issues I've had with them in Python. As they are just buried in plain strings, there's no validation of their syntax until you hit the line of code that tried to use them only to discover that Python 3.12 has changed the syntax and what was once working is now broken. I'd love to see this validated at compile-time/load-time of any language to avoid those unexpected…

C# has compile-time regex, which are turned into fairly reasonable code doing the matching you can even inspect. The main goal isn't to have the syntax verified during compilation (technically it happens even during editing the code), but rather to reduce either dependencies on complex code at runtime, while still maintaining good performance by using the complex regex.

Re: Implementing Regular Expressions in TypeScript Types (Badly)

#4

Post by nsonha »

ygra wrote: post #3
penguin359 wrote: post #2

Having compile-time RegEx's would certainly fix some issues I've had with them in Python. As they are just buried in plain strings, there's no validation of their syntax until you hit the line of code that tried to use them only to discover that Python 3.12 has changed the syntax and what was once working is now broken. I'd love to see this validated at compile-time/load-time of any language to avoid those unexpected…

C# has compile-time regex, which are turned into fairly reasonable code doing the matching you can even inspect. The main goal isn't to have the syntax verified during compilation (technically it happens even during editing the code), but rather to reduce either dependencies on complex code at runtime, while still maintaining good performance by using the complex regex.

This article isn't about compile-time regex (which is in many languages, including javascript) though? It's compile-time regex MATCHING.

Re: Implementing Regular Expressions in TypeScript Types (Badly)

#5

Post by asicsp »

penguin359 wrote: post #2

Having compile-time RegEx's would certainly fix some issues I've had with them in Python. As they are just buried in plain strings, there's no validation of their syntax until you hit the line of code that tried to use them only to discover that Python 3.12 has changed the syntax and what was once working is now broken. I'd love to see this validated at compile-time/load-time of any language to avoid those unexpected…

If you need to detect syntax issues, you can use `re.compile()`. For example, before Python 3.11, you'll get an error:

    >>> re.compile(r'\w++')
    re.error: multiple repeat at position 3
To use such a compiled pattern, you can call the method on this object instead of `re`. For example:

    >>> word = re.compile(r'\w+')
    >>> word.findall('hello-there!')
    ['hello', 'there']

Re: Implementing Regular Expressions in TypeScript Types (Badly)

#6

Post by JonChesterfield »

It's regular expressions via derivatives which is sanely representable in functional programming fashion. Matching a single string doesn't need the caching layers for termination, you could do this in C++ templates if you have the patience. Nice to see it in typescript syntax.

Re: Implementing Regular Expressions in TypeScript Types (Badly)

#7

Post by hombre_fatal »

asicsp wrote: post #5
penguin359 wrote: post #2

Having compile-time RegEx's would certainly fix some issues I've had with them in Python. As they are just buried in plain strings, there's no validation of their syntax until you hit the line of code that tried to use them only to discover that Python 3.12 has changed the syntax and what was once working is now broken. I'd love to see this validated at compile-time/load-time of any language to avoid those unexpected…

If you need to detect syntax issues, you can use `re.compile()`. For example, before Python 3.11, you'll get an error: >>> re.compile(r'\w++') re.error: multiple repeat at position 3 To use such a compiled pattern, you can call the method on this object instead of `re`. For example: >>> word = re.compile(r'\w+') >>> word.findall('hello-there!') ['hello', 'there']

The existent of re.compile is compatible with and doesn’t address their complaint.

Re: Implementing Regular Expressions in TypeScript Types (Badly)

#10

Post by skalt »

evolveyourmind wrote: post #9

Nice! My version: https://github.com/desi-ivanov/ts-regexp

That's a great concise implementation! I'm glad you also went with the parse-and-interpret-an-AST approach: it seems like the right design. Your `Reconstruct` type is a great idea! I might copy that.
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