Curry things in lua! TODO: make this less terrible, or just don't use it, gosh.

curry.lua

local function dummy()end
local funcmt = getmetatable(dummy)
if not funcmt then
  funcmt = {}
  debug.setmetatable(dummy,funcmt)
end
funcmt.__index = funcmt.__index or {}
local type,select = type,select
assert(type(funcmt.__index) == "table")
 
local function curry(f, ...)
  if(select("#", ...) == 0) then
    return f
  else
    local first_arg = select(1, ...)
    local function onearg(...)
      return f(first_arg, ...)
    end
    return curry(onearg, select(2, ...))
  end
end
 
local function rotate_left_internal(howmuch, idx, n, ...)
  if n == idx then return end
  return select(((idx + howmuch) % n) + 1, ...),
    rotate_left_internal(howmuch, idx + 1, n, ...)
end
 
local function rotate_left(howmuch, ...)
  local n = select("#", ...)
  return rotate_left_internal(howmuch, 0, n, ...)
end
 
-- for some reason I thought this would help???
--[[local function reverse_internal(idx, n, ...)
  if n == idx then return end
  return select(n - idx, ...), reverse_internal(idx + 1, n, ...)
end
 
local function reverse(...)
  local n = select("#", ...)
  return reverse_internal(0, n, ...)
end--]]
 
local function rcurry(f, ...)
  local n = select("#", ...)
  return curry(function(...)
    return f(rotate_left(n, ...))
  end, ...)
end
 
funcmt.__index.curry = curry
funcmt.__index.rcurry = rcurry
 
print:rcurry(6,7,nil):curry(1,2,3)(4,5)
-- equivalent to print(1,2,3,4,5,6,7,nil)