Re: Implementing help function (like in Python)
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- Subject: Re: Implementing help function (like in Python)
- From: David Manura <dm.lua@...>
- Date: 2007年9月15日 00:19:31 -0400
Matias Guijarro wrote:
I would like to implement...like Python docstrings...
> I think a possible solution would be to use the debug library
> (debug.getinfo) to find the source file and to extract a kind of
> "docstring" out of the function code.
This can be done using weak tables in a way that avoids source
processing and debug:
-- docstring.lua
local M = {}
local docstrings = setmetatable({}, {__mode = 'kv'})
function M.set(obj, str)
docstrings[obj] = str
return obj
end
function M.get(obj) return docstrings[obj] end
function M.help(obj) print(M.get(obj)) end
-- optional syntax simplification
local mt = {__concat = function(self, obj)
return M.set(obj, self[1]) end}
setmetatable(M, {__call = function(_, str)
return setmetatable({str}, mt)
end})
return M
-- test.lua (example)
local docstring = require 'docstring'
local square =
docstring[[Square a number.]] ..
function(x)
return x * x
end
assert(square(5) == 25)
assert(docstring.get(square) == 'Square a number.')
docstring.help(square) -- prints "Square a number."
docstring.set(square, 'calcular el cuadrado de un número')
assert(docstring.get(square) == 'calcular el cuadrado de un número')
assert(docstring.get(print) == nil)
One reason '..' is chosen is because it is right associative, which
allows additional decorators (besides docstrings) to be applied to an
object as well.