[R-SIG-Mac] UI suggestion: allow a tab with no more suggestions to fill in "$"

[Simon Urbanek]

> On May 24, 2016, at 4:09 PM, Timothy Bates <tim.bates at ed.ac.uk> wrote:
> 
> 
> On 24 May 2016, at 12:59 am, Simon Urbanek <simon.urbanek at r-project.org> wrote:
>> how should be determine that you want $? If it's a matrix, maybe you want [ ... if it's a function maybe you want ( ... it looks like a hornet's nest to me, but if you provide logic, we may be able to code it up ;)
>> Cheers, Simon
> 
> Hi Simon,
> 
> My logic is as follows:
> 
> 1. When a name is already complete, when the user pushes tab again, they are expecting “more” name completion, i.e.,  they want to access a $ or @ sub-component.


That seems like a very strong assumption and my point questioning that assumption. For a lot of objects $ makes no sense which is why I'm reluctant to add $ unconditionally. Really, it only makes sense for lists (and some subclasses) - anything else gets a bit dodgy (it works for some but not others).

That said, I suppose one possible approach would be to catch any completion that yields just the items itself and if that happens attempt a completion with $ appended and see what it yields. If it yields anything additional, return that result instead. You can test whether you like that by using something like the following:


add.fn("rcompgen.completion", function (x)
{
    comp <- function(x) {
         utils:::.assignLinebuffer(x)
         utils:::.assignEnd(nchar(x))
         utils:::.guessTokenFromLine()
         utils:::.completeToken()
         utils:::.CompletionEnv[["comps"]]
    }
    res <- unique(comp(x))
    if (nzchar(x) && identical(res, x) && !identical(substr(x, nchar(x), nchar(x) + 1L), "$")) {
       rc <- comp(paste0(x, "$"))
       if (!identical(substr(rc, nchar(rc), nchar(rc) + 1L), "$")) res <- rc
    }
    res
})

Obviously, you can eve spin that further and carry on with @ if $ doesn't work.

Cheers,
Simon





> Currently, nothing happens, and the user feels “thwarted”… like the typing “Simon" but then having to type a space and a tab to get "Urbanek" :-)
> 
> 2. Most object components are $ indexed rather than @ indexed), so $ is the best guess.
> 
> Based on this, a simple logic of "append $ if the current name is a valid name" would be an advance in many cases. I can’t see a downside.
> 
> A smarter logic would call .DollarNames() on the current word and if it found $ items, then append the $ and display the dropdown, if not, beep.
> 
> Re “why not offer mtcars[] instead of mtcars$”? or adding the round brackets to a function, I think the answer is that while perhaps an appropriately smart version of rcompgen could support this, users are expecting tab completion to complete names and in R, that means a complete addressable name for an object component.
> 
> So I think that having tab add a $ accessor would seem natural, whereas having one tab complete the name, and the next one add brackets would not.
> 
> Currently, I find that the mental context switch from completing a name to accessing or filling in parameters is sufficiently “different” that typing the bracket ending seems natural, and it’s nice that R.app gives us the closing bracket for free.
> 
> Cheers, tim
> 
> https://stat.ethz.ch/R-manual/R-devel/library/utils/html/rcompgen.html
> 
> PS: Indeed, a type-aware completion system would be great (as you imply). I enjoy the feature in RStudio now where valid completions are given, for instance, within a square bracket context. i.e., mtcars[1,⇥] gives a drop down of column names - much easier than running names() in the terminal to remember what is what.
> 
> 
>> 
>> On May 20, 2016, at 8:08 AM, Timothy Bates <tim.bates at ed.ac.uk> wrote:
>>> Like most of us I am sure, I use the tab completion system a lot, not just to complete object names, but to pick from the drop-list created when one hits tab after a $ sign.
>>> 
>>> Current situation to get to  "object$part1$level2” the user currently has to type:
>>> 1. "obj→" (completed to "object")
>>> 2. Type "$→" and pick part1
>>> 3. Type "$→" and pick level2
>>> 
>>> Suggestion: make a second "tab" press fill in the $-sign. That would reduce the above to:
>>> 1. "obj→" (completed to "object")
>>> 2. Type "→ →" and pick part1
>>> 3. Type "→ →" and pick level2
>>> 
>>> MUCH quicker, as the dollar sign involves lifting finger off tab key, hitting (for English) shift-4 (a two hand operation, or an awkward one-hand stretch), then moving back to the tab key.
>>> 
>>> Users of the @ accessor  might feel left out - perhaps give them shift-tab :-)
>>> 
>>> PS: Still be nice bump up the font size in the bottom tool-tip bar, if only back to the old physical height (or perhaps just re-use the RStudio tool-tip completion system)
> 
> 
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