fix: forgot of course i would never be 0 `const dsl = (chunks, ...rest) => chunks.reduce((s, c, i) => s + rest[i-1] + c);`
VS `const dsl = (chunks, ...rest) => chunks.reduce((s, c, i) => s + (dsl[Symbol.templateTag] || String)(rest[i-1]) + c);` On Fri, Nov 18, 2016 at 12:56 AM, Andrea Giammarchi < andrea.giammar...@gmail.com> wrote: > I'm not fully sure I understand ... instead of: > > ```js > const dsl = (chunks, ...rest) => chunks.reduce((s, c, i) => s + (i ? > rest[i-1] : '') + c); > ``` > > you are looking for something similar ? > > ```js > const dsl = (chunks, ...rest) => chunks.reduce((s, c, i) => s + ( > i ? (dsl[Symbol.templateTag] || String)(rest[i-1]) : '' > ) + c); > ``` > > if that's the case, is `Symbol.templateTag` really needed ? > > It looks to me it's possible to define your own behavior through your own > transformer already and this proposal easily brings parsing-method clashing > in the plate. > > Or maybe not ... like I've said, I haven't fully understood the issue. > > Thanks for any sort of extra clarification. > > Regards > > > On Fri, Nov 18, 2016 at 12:30 AM, Alexander Jones <a...@weej.com> wrote: > >> OK, I was thinking about this incorrectly and I think you're right - it >> doesn't Break The Web. It's exactly the same as when @@isConcatSpreadable >> and @@toStringTag were introduced, as far as I can tell. >> >> If no-one has any obvious objections to save me the effort, I'll try to >> write up a stage 0 this weekend. >> >> Thanks >> >> >> >> On 17 November 2016 at 04:58, Mark S. Miller <erig...@google.com> wrote: >> >>> Hi Alexander, I have run into this myself. It is a real problem, and I >>> like the nature of your proposed solution. But I don't understand how it >>> might break the web. If Symbol.templateTag is a new symbol, guaranteed >>> unequal to any prior value, how can introducing it, and new behavior >>> conditional on it, change any existing behavior? >>> >>> >>> >>> >>> On Wed, Nov 16, 2016 at 5:02 PM, Alexander Jones <a...@weej.com> wrote: >>> >>>> Hi es-discuss! >>>> >>>> Template tags are a great feature with many novel applications, IMO >>>> approaching macro-level expressiveness. But due to their nature in this >>>> context, it's helpful if tags are named quite tersely. Unfortunately, if >>>> you have existing API, this can be challenging. >>>> >>>> Let's say I have a DSL (domain-specific language), and I *may*, >>>> unsafely, generate typed snippets of code containing that DSL like so: >>>> >>>> ```js >>>> function dsl(code: string) { >>>> // `code` MUST be well-formed >>>> } >>>> >>>> const someStatement = dsl("val foo = " + dslEncode(foo)); >>>> ``` >>>> >>>> Let's say I'd like to add support in my library for ES6 clients such >>>> that they can do: >>>> >>>> ```js >>>> const someStatement = dsl`val foo = ${foo}`; >>>> ``` >>>> >>>> where the `dsl` template tag would be implemented such that `dslEncode` >>>> is used on each interpolated expression. >>>> >>>> Unfortunately, the `dsl` function's arguments are already defined and >>>> can't be changed. I'd need a new name, like `dsl.tag`, which would end up >>>> being a fair bit more verbose. >>>> >>>> Would it be possible, at this point, to introduce a new behaviour into >>>> ES such that instead of merely calling the tag object, the implementation >>>> first checks for a `Symbol.templateTag` property on the tag object, and if >>>> it exists, it is invoked? I'd guess this can't Break The Web because no-one >>>> can realistically be using an existing function as a template tag if it was >>>> not already designed for it. >>>> >>>> ```js >>>> const someStatement = dsl`val foo = ${foo}`; >>>> // desugars to, approximately >>>> const someStatement = (dsl[Symbol.templateTag] || dsl)(["val foo =", >>>> ""], foo); >>>> ``` >>>> >>>> To be honest, I am kind of surprised it wasn't already implemented like >>>> this, but maybe there were performance concerns with the branching. >>>> Interested in your thoughts. >>>> >>>> Thanks >>>> >>>> Alex >>>> >>>> _______________________________________________ >>>> es-discuss mailing list >>>> es-discuss@mozilla.org >>>> https://mail.mozilla.org/listinfo/es-discuss >>>> >>>> >>> >>> >>> -- >>> Cheers, >>> --MarkM >>> >> >> >> _______________________________________________ >> es-discuss mailing list >> es-discuss@mozilla.org >> https://mail.mozilla.org/listinfo/es-discuss >> >> >
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