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The functions in this module return other functions, namely iterators. It also contains utility functions for functional programming.


local p = {}

function p.identity(...)
	return ...
end

function p.memoize(fn)
	local cache = {}
	return function(...)
		local key = mw.dumpObject({...})
		if not cache[key] then
			cache[key] = fn(...)
		end
		return cache[key]
	end
end

function p.negate(fn)
	return function(...)
		return not fn(...)
	end
end

function p.noop() 
	return nil
end

function p.peek(tbl)
	mw.logObject(tbl)
	return tbl
end

function p.pipe(...)
	local state = {...}
	return function(functions)
		for _, fn in ipairs(functions) do
			state = {fn(unpack(state))}
		end
		return unpack(state)
	end
end

-- http://lua-users.org/wiki/RangeIterator
function p.range(a, b, step)
  if not b then
    b = a
    a = 1
  end
  step = step or 1
  local f =
    step > 0 and
      function(_, lastvalue)
        local nextvalue = lastvalue + step
        if nextvalue <= b then return nextvalue end
      end or
    step < 0 and
      function(_, lastvalue)
        local nextvalue = lastvalue + step
        if nextvalue >= b then return nextvalue end
      end or
      function(_, lastvalue) return lastvalue end
  return f, nil, a - step
end

return p
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