String iterpolation about slint HOT 7 CLOSED

From an implementation point of view, one would need to adjust the lexer to split the string in token that can be parsed independently: StringLiteral OpenInterpolation Identifier Dot Identifier ... CloseInterpolation StringLiteral OpenInterpolation ...
Then the parser could build an expression tree that would have a Expression::InterpolatedString { components: Vec<Expression> } that would then be produced.

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Thanks for the implementation view, will take a closer look on it soon.

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Using a \ for the interpolation syntax is confusing to me. I'd expect it to be used to disable a special syntax, rather than mark it. I'd prefer "{foo}" to be interpolated, like Python's f strings.

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Ah yes, Python's f strings are like JS template strings - I also like that syntax a lot. And using regular quotes is easier than the backticks in JS. The more I think about it, the more I dislike those and prefer something like f strings.

I guess we just have to pick one and go with it.

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I tried to make a survey of the different language:
Please let me know if i got something wrong or forgot a language.
I only include the languages that allow to put any arbitrary expression within a string, so not just printf style

Javascript

Uses ` instead of " for the quote, then ${ ... } for the expression

`string text ${expression} string text`

Python

Require a f before the string, then expression are just in { }

f'My name is {name}, my age next year is {age+1}, my anniversary is {anniversary:%A, %B %d, %Y}.'

C# / VisualBasic

String starts with $ and then inside is just { }

$"Hello, {name}! Today is {date.DayOfWeek}, it's {date:HH:mm} now."

PHP

One must use " (and not ') then one can use $variable or ${variable}
One can put some expression within the ${ ... } but not all expression are supported.

"This works {$obj->values[3]->name}";

Swift

Normal string using \( ... )

"\(multiplier) times 2.5 is \(Double(multiplier) * 2.5)"

Rust

Rust does not have string interpolation, but the syntax of the format! macro will allow to use {variable} as per RFC 2795

Note that in the .60 language, there is not even yet way to escape quotes or anything. We don't have raw literal either.
But I guess that \ would be the most natural character to do escapes, since this is what almost all languages do (eg: \n and \") so it would be natural to use \{ }, then one does not need anything else special. This is almost what swift does.

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I vote for python or javascript, maybe a mix between both languages since they are the cleaner and friendly approach for the user ?

// js
`string text ${expression} string text`
// python
f"string text {expression} string text"
// mix
`string text {expression} string text` or "string text {expression} string text"

I also agree with @Plecra comment about the escape char for interpolation.

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Currently what's implemented in master is "string text \{expression} string text"

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