Re: argument alternative
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- Subject: Re: argument alternative
- From: Pierre-Yves Gérardy <pygy79@...>
- Date: 2010年2月24日 12:43:26 +0100
Here's some code I use in LÖVE to solve a similar problem, but with a
different approach:
In LÖVE, all functions that take a color as input actually simply take
r,g,b,a parameters (range 0-255)
So I use a variation on the tupple pattern.
red = color.rgba(255,0,0)
you can pass around the red object, and then call red() where you want
to unpack it.
setColor(red())
is translated to
setColor(255,0,0,255)
The API works as follows:
solidGrey=color.rgba(192)
translucentGrey=color.rgba(192,128)
solidGrey() -- => 192,192,192,255
translucentGrey() -- => 192,192,192,128
solidGreen=color.rgba(0,255,0)
translucentGreen=color(0,255,0,128)
solidGreen() -- => 0,255,0,255
solidGreen(64) -- => 0,255,0,64
solidRed=color.hsla(0)
color.setAlpha(169)
solidRed() -- => 255,0,0,169
pink = color.hsla(0,192,255)
blue = color.rgba("#0000ff")
-- The code:
function arityfunction( T, error_ )
if error_ then
setmetatable( T, {__index=function( t, i ) error( tostring( error_ ) ) end} )
end
return function(...)
return T[#{...}](...) -- the use of #{...} is intentional.end
end
end
do
color={}
local globalalpha=255
color.setAlpha=function( alpha ) globalalpha=alpha end
local function createColorObject(r,g,b,a)
-- you can use the weak table trick from the PiL
-- to memoize your color objects if you want to.
return function( alpha )
return r, g, b, alpha and alpha or a or globalalpha
end
end
local _rgba=arityfunction( {
[1]=function(i) return createColorObject(i,i,i) end,
[2]=function(i,a) return createColorObject(i,i,i,a) end,
[3]=function(r,g,b) return createColorObject(r,g,b) end,
[4]=function(r,g,b,a) return createColorObject(r,g,b,a) end
},"color.rgba() accepts 1 to 4 parameters")
function color.rgba(...)
local s, alpha = {...}[1], {...}[2]
if type(s)=="string" then
local r,g,b
-- process your string here
error("the \"#rrggbb\" syntax isn't implemented yet")
return createColorObject(r, g, b, alpha)
else
return _rgba(...)
end
end
local function _hsla(h,s,l,a)
local r,g,b
-- convert hsl to rgb here
error("_hsla isn't impelemented yet")
return createColorObject(r,g,b,a)
end
color.hsla=arityfunction({
[1]=function(h) return _hsla(h,255,255) end,
[2]=function(h,a) return _hsla(h,255,255,a) end,
[3]=function(h,s,l) return _hsla(h,s,l) end,
[4]=function(h,s,l,a) return _hsla(h,s,l,a) end
},"color.hsla() accepts 1 to 4 parameters")
end
I hope this helps :-)
Cheers,
Pierre-Yves