fun: add fun.partial and fun.flip

1 files changed, 37 insertions, 0 deletions

diff --git a/src/luarocks/fun.lua b/src/luarocks/fun.lua
index dfdf36ed..b1740833 100644
--- a/src/luarocks/fun.lua
+++ b/src/luarocks/fun.lua
@@ -2,6 +2,8 @@
 --- A set of basic functional utilities
 local fun = {}
 
+local unpack = table.unpack or unpack
+
 function fun.concat(xs, ys)
    local rs = {}
    local n = #xs
@@ -63,4 +65,39 @@ function fun.sort_in(t, f)
    return t
 end
 
+function fun.flip(f)
+   return function(a, b)
+      return f(b, a)
+   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(table.unpack(args, 1, n+m))
+      end
+   end
+end
+
 return fun