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|
--- A set of basic functional utilities
local fun = {}
local unpack = table.unpack or unpack
function fun.concat(xs, ys)
local rs = {}
local n = #xs
for i = 1, n do
rs[i] = xs[i]
end
for i = 1, #ys do
rs[i + n] = ys[i]
end
return rs
end
function fun.contains(xs, v)
for _, x in ipairs(xs) do
if v == x then
return true
end
end
return false
end
function fun.map(xs, f)
local rs = {}
for i = 1, #xs do
rs[i] = f(xs[i])
end
return rs
end
function fun.filter(xs, f)
local rs = {}
for i = 1, #xs do
local v = xs[i]
if f(v) then
rs[#rs+1] = v
end
end
return rs
end
function fun.traverse(t, f)
return fun.map(t, function(x)
return type(x) == "table" and fun.traverse(x, f) or f(x)
end)
end
function fun.reverse_in(t)
for i = 1, math.floor(#t/2) do
local m, n = i, #t - i + 1
local a, b = t[m], t[n]
t[m] = b
t[n] = a
end
return t
end
function fun.sort_in(t, f)
table.sort(t, f)
return t
end
function fun.flip(f)
return function(a, b)
return f(b, a)
end
end
function fun.find(xs, f)
if type(xs) == "function" then
for v in xs do
local x = f(v)
if x then
return x
end
end
elseif type(xs) == "table" then
for _, v in ipairs(xs) do
local x = f(v)
if x then
return x
end
end
end
end
function fun.partial(f, ...)
local n = select("#", ...)
if n == 1 then
local a = ...
return function(...)
return f(a, ...)
end
elseif n == 2 then
local a, b = ...
return function(...)
return f(a, b, ...)
end
else
local pargs = { n = n, ... }
return function(...)
local m = select("#", ...)
local fargs = { ... }
local args = {}
for i = 1, n do
args[i] = pargs[i]
end
for i = 1, m do
args[i+n] = fargs[i]
end
return f(unpack(args, 1, n+m))
end
end
end
function fun.memoize(fn)
local memory = setmetatable({}, { __mode = "k" })
local errors = setmetatable({}, { __mode = "k" })
local NIL = {}
return function(arg)
if memory[arg] then
if memory[arg] == NIL then
return nil, errors[arg]
end
return memory[arg]
end
local ret1, ret2 = fn(arg)
if ret1 ~= nil then
memory[arg] = ret1
else
memory[arg] = NIL
errors[arg] = ret2
end
return ret1, ret2
end
end
return fun
|
