Hacker News Reader

Purity and practicality are at odds and every language finds a different balance between the two. There is no one correct balance so busy minds will inevitably have loud opinions they want accepted as the one correct balance.

> busy minds

cute pun but compared to busybodies it really hides the implication (i thought you were talking about people with adhd at first).

> One option, which Python and C# both picked is, well, leave it to taste.

Every time I need to format a number or a date in C#, I just hit the documentation. I refuse to memorize its terrible formatting mini language.

Or you could just write your own if you think you can create one you'll be happier with. C# provides IFormatProvider for this exact purpose and I've honestly not seen that level of customizability elsewhere.

> String interpolation is one of those features

70% of these "wtfs" aren't about string interpolation but just python's syntax for string.format

https://docs.python.org/3/library/string.html#format-string-...

"String interpolation" is a term for the purpose that the string.format syntax serves.

no it's not - string interpolation means inlining values and such. format strings long predate string interpolation https://en.wikipedia.org/wiki/Printf

Python 2.7 called its % operator the "string interpolation" operator[1], and it doesn't allow inline values.

[1]: https://docs.python.org/2.7/library/stdtypes.html#string-for...

  > then one day you realise you're looking at unintelligible nonsense and you say "Oh no, what have we done?"

I think that’s a bit of what the Java String Template folks went through.

It was a pretty cool system (on the surface, not having used it, I liked what I saw), but they pulled it straight out. They felt the direction was unworkable. Pretty interesting considering I think the demand for such a facility (as mentioned, once tasted, hard to let cider), plus the work involved to date. Interesting they found it irredeemable to shelve it entirely and back to the white board.

I tend to stuff complicated strings (SQL queries and such) into resources (files that get baked into the JAR) and implement some kind of templating for them if I think it's necessary.

With proper escape (un-taint) on any user input, right?

Of course. If it is SQL you ride on JDBC already supporting placeholders, so there isn't any need for you to support substitutions for ordinary SQL.

If you want to do more complex "Dynamic SQL", say you are writing a query builder where people can fill out fields to do a complex query, your best bet is JooQ, which I use heavily at work.

I hate Rust's solution because it's not a solution at all.

Interpolation only works in a small subset of cases, which makes you constantly having to think whether it can or can't be used in the current situation and requires endless churn when refactoring code.

At the very minimum, they need to allow it to work with field access.

On the other hand, in python, while examples like this site exist and are funny/weird/quirky in practice nobody cares, and they just enjoy using fstrings.

It's pretty straightforward? You can interpolate a variable in scope and apply modifiers to it. You can't interpolate arbitrary expressions (which field access would be). Alternatively, you can interpolate an arbitrary identifier, then specify a value for that identifier in the arguments.

The key is "identifiers, not expressions."

The person you're responding to didn't misunderstand (or ask) how it works. They just find it inconvenient.

It would be perfectly possible to add field access without needing to support arbitrary expressions. However, as someone coming from a C# background, I would very much prefer arbitrary expressions.

> then you add more, each step seems like it's an improvement, and then one day you realise you're looking at unintelligible nonsense and you say "Oh no, what have we done?"

I've never found it difficult to keep them in check. I still can't fathom a use case for nesting f-strings within an f-string substitution, for example. And probably the only format specifier I commonly use is `:02x`.

> I still can't fathom a use case for nesting f-strings within an f-string substitution

Isn't that mostly just a side effect of using the proper full python parser for F-strings? The syntax for what was allowed inside an F-string kept getting more and more permissive, until they just decided to permit ~all of python inside an F-string.

> CS would love to have as much of whatever as we can, but mathematics says no

What does this have to do with either topic?

I, too, struggled to understand the meaning of this sentence. I can parse it, I guess, but any meaning I try to guess for it is either implausible or irrelevant.

Take optimisation, another task like interpolation which the machine does to transform our program text into an executable

We'd like exhaustive optimisation, in fact that can't be done and today we're used to a relatively aggressive optimisation which would not have been possible fifty years ago, but we're nowhere close to optimal for non-trivial programs.

Or correctness, it seems as though global static analysis should be possible, at least for something modest like a typical Unix utility - nope, that is known to be mathematically impossible for even quite modest software, only local analysis is at least plausible and its effects are much more limited than we might hope.