Anonymous user
Currying: Difference between revisions
m
→{{header|Lua}}: another implementation
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m (→{{header|Lua}}: another implementation) |
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Line 1,103:
local adder = curry2(add)
assert(adder(3)(4) == 3+4)
local add2 = adder(2)
assert(add2(3) == 2+3)
assert(add2(5) == 2+5)
</lang>
== another implementation ==
Proper currying, tail call without array packing/unpack.
<lang lua>
local curry do
local call = function(fn,...)return fn(...)end
local fmt,cat,rawset,rawget,floor = string.format,table.concat,rawset,rawget,math.floor
local curryHelper = setmetatable({},{
__call = function(me, n, m, ...)return me[n*256+m](...)end,
__index = function(me,k)
local n,m = floor(k / 256), k % 256
local r,s = {},{} for i=1,m do r[i],s[i]='_'..i,'_'..i end s[1+#s]='...'
r,s=cat(r,','),cat(s,',')
s = n<m and fmt('CALL(%s)',r) or fmt('function(...)return ME(%d,%d+select("#",...),%s)end',n,m,s)
local sc = fmt('local %s=... return %s',r,s)
rawset(me,k,(loadstring or load)(sc,'_',nil,{CALL=call,ME=me,select=select}) )
return rawget(me,k)
end})
function curry(...)
local pn,n,fn = select('#',...),...
if pn==1 then n,fn = debug.getinfo(n, 'u'),n ; n = n and n.nparams end
if type(n)~='number' or n~=floor(n)then return nil,'invalid curry'
elseif n<=0 then return fn -- edge case
else return curryHelper(n,1,fn)
end
end
end
-- test
function add(x,y)
return x+y
end
local adder = curry(add) -- get params count from debug.getinfo
assert(adder(3)(4) == 3+4)
local add2 = adder(2)
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