passing common keywords to nested functions

[berceanu]

I often find myself passing long lists of parameters from one function to another. A simple, contrived example would be the following

function fun3(; kw1 = 1, kw2 = 2, kw5 = 8, kw6 = 4)
    fun2(; kw1 = kw1, kw2 = kw2)
end
function fun2(; kw1 = 1, kw2 = 2)
    fun1(; kw1 = kw1, kw2 = kw2)
end
function fun1(; kw1 = 1, kw2 = 2, kw3 = 3)
    kw1 + kw2 + kw3
end

This results in code which is not easy to maintain. Notice that kw1 and kw2 are common to all 3 functions. The way the code is written now, if I decide I want kw3 of fun1 to be accesible from fun3, I need to do:

function fun3(; kw1 = 1, kw2 = 2, kw5 = 8, kw6 = 4, kw3=3)
    fun2(; kw1 = kw1, kw2 = kw2, kw3=kw3)
end
function fun2(; kw1 = 1, kw2 = 2, kw3=3)
    fun1(; kw1 = kw1, kw2 = kw2, kw3=kw3)
end
function fun1(; kw1 = 1, kw2 = 2, kw3 = 3)
    kw1 + kw2 + kw3
end

Suggestions for improving current behavior are welcome :)

[StefanKarpinski]

This is related to the fact that function taking keyword arguments are hard to deprecate: you can add a deprecation for a now-regretted method of a function easily and in a separate deprecations file; if you want to deprecate keywords for a function, there's no clean easily separable way to do it.

[johnmyleswhite]

One potential solution is to allow one to define groups of keywords and allow groups to passed around atomically.

[StefanKarpinski]

Yeah, that's a good way to go, but I'm not sure how to express that.

[johnmyleswhite]

Seems like you need syntax: f(x, y, $a(kw1 = 1, kw2 = 2)) = g(x + y, $a) with a better group indicator might get you started.

[tonyhffong]

or apply( f, args; params=d ) where d is typed Dict{Symbol,Any}

[PythonNut]

Doesn't Julia already support splatting a Dict{Symbol,Any} (or is it Dict{String,Any}?) as keyword arguments.

We do still need a syntax for capturing a group. Syntax for that is up for grabs.

[JeffBezanson]

Yes splatting a Dict works.

[SimonDanisch]

This is a huge thing for me as well. My work around:

immutable Style{StyleValue}
end
mergedefault!{S}(style::Style{S}, styles, customdata) = merge!(styles[S], Dict{Symbol, Any}(customdata))
#Text Rendering:
TEXT_DEFAULTS = [
:Default => [
  :start            => Vec3(0),
  :offset           => Vec2(1, 1.5), #Multiplicator for advance, newline
  :color            => rgbaU8(248.0/255.0, 248.0/255.0,242.0/255.0, 1.0),
  :backgroundcolor  => rgbaU8(0,0,0,0),
  :model            => eye(Mat4),
  :newline          => -Vec3(0, getfont().props[1][2], 0),
  :advance          => Vec3(getfont().props[1][1], 0, 0),
  :camera           => pcamera
]
]
# High Level text rendering for one line or multi line text, which is decided by searching for the occurence of '\n' in text
visualize(text::String,                 style=Style(:Default); customization...) = visualize(style, text, mergedefault!(style, TEXT_DEFAULTS, customization))
# Low level text rendering for one line text
visualize(text::Texture{GLGlyph, 1, 1}, style=Style(:Default); customization...) = visualize(style, text, mergedefault!(style, TEXT_DEFAULTS, customization))
# Low level text rendering for multiple line text
visualize(text::Texture{GLGlyph, 1, 2}, style=Style(:Default); customization...) = visualize(style, text, mergedefault!(style, TEXT_DEFAULTS, customization))