From fbb3431367a145e73bd038b0c779fd8355c997b4 Mon Sep 17 00:00:00 2001
From: Hisham Muhammad <hisham@gobolinux.org>
Date: Thu, 28 Mar 2019 23:38:07 -0300
Subject: fun: add find and memoize functions

---
 src/luarocks/fun.lua | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/src/luarocks/fun.lua b/src/luarocks/fun.lua
index c37a5d4b..10d8d446 100644
--- a/src/luarocks/fun.lua
+++ b/src/luarocks/fun.lua
@@ -71,6 +71,24 @@ function fun.flip(f)
    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
@@ -101,4 +119,26 @@ function fun.partial(f, ...)
    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
-- 
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