[InflexHQ]

> Another thought along these lines: quite a lot of my spreadsheet use involves doing calculations on whole columns. This is really painful in Excel, where I have to manually select just the right areas of my sheet, then write the formula—without disturbing my selections!—making sure of course that I put the result in a place where it fits. And this just gets worse with more data. In my own proof-of-concept, I implement broadcasting of all functions over arrays (à la APL or MATLAB), which makes this a lot easier, and is quite possibly the best UX improvement I’ve found. Do you have any plans to do something like this in Inflex? (I know it already has higher-order functions, but e.g. `voltage / current` is a lot easier to read and write than `zipwith(x y:x/y, voltage, current)`…)

I haven’t seriously put thought into that use-case. There’s the facility via type classes, but I’m not sure what the trade offs are with that kind of overloading. The same question applies to FRP behaviors and events. Do you explicitly require a map or list comprehensions or do you “broadcast” automatically, and if you do, what are the pitfalls?

I have put some thought into something related which is aggregations. On a given table I want to be able to add a column which implements any mapAccum over the table, such as balance over time. The code generated would be table.accum(state: row: state + row.x) for example. The UI would make it easy to pick common accumulators and folds, but also trivial to write an expression. Your voltage current example would work like that.

This arrays-of-records overlaps a bit with your records-of-arrays naturally. The two are often considered sides of the same coin and I’ve thought about using RoA internally for efficiency, but “broadcasting” to make that nice didn’t occur to me. The written simplicity is compelling, for sure.

> From my perspective, they’re definitely worth it: most of my biggest Excel mistakes have involved botched unit conversions. (If it matters, my background is physics and chemistry; most of my spreadsheet usage has been for assignments throughout my degree.)

Yeah, it’s definitely a valuable thing, I’m just not sure about the trade offs. At some point you have to stop adding features to the language, and that one didn’t convince me enough at the time.

> applying substitutions at the same time as unification

Right, I’ve seen that also on a language we develop at work. Incidentally this is needed if you want to combine two row types and assign a type to the expression.

> If it helps, I’d be more than happy to help out with development! This is an area I find incredibly interesting to work on, but my own attempt never really got past the proof-of-concept stage, and I consider duplicate development a bit of a waste.

I might only have time to discuss ideas and no time to collaborate on dev right now, but happy to swap contact details. If you drop a mail [e-mail] I’ll reply via my personal email.

[bradrn]

> I haven’t seriously put thought into that use-case. … Do you explicitly require a map or list comprehensions or do you “broadcast” automatically, and if you do, what are the pitfalls?

It’s all automatic. Basically, any function a→b can be used as [a]→[b], [[a]]→[[b]], and so on; functions with multiple arguments work similarly. In the intermediate language, each argument is then annotated with the amount by which it needs to be lifted. (So e.g. if `xs : [Int]`, then `10/xs` gets translated to something like `(/)({10,1}, {xs,0})`.

As for pitfalls… well, I haven’t encountered all that many yet. The implementation is a little unprincipled at this point, but there’s probably some way to make it more rigorous. It’s basically as close as I can get to J or MATLAB in a typed language, and people don’t often have problems with broadcasting in those languages.

> I have put some thought into something related which is aggregations. On a given table I want to be able to add a column which implements any mapAccum over the table, such as balance over time. The code generated would be table.accum(state: row: state + row.x) for example. The UI would make it easy to pick common accumulators and folds, but also trivial to write an expression. Your voltage current example would work like that.

This does sound quite similar to what I’m doing, though perhaps more limited.

> Incidentally [applying substitutions at the same time as unification] is needed if you want to combine two row types and assign a type to the expression.

Hmm, interesting. You don’t happen to have a link, do you? (Though I seem to recall hearing TAPL has something about this… I really do need to read it one of these days.)

> I might only have time to discuss ideas and no time to collaborate on dev right now, but happy to swap contact details. If you drop a mail [e-mail] I’ll reply via my personal email.

Sure, that sounds great! I’ll send you an email now.