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Comment by wahern | Hacker News Reader

String trim is just:

  foo:gsub("%s*$", "")

  foo:gsub("^%s*", "")

The standard idiom for OOP in Lua is a one-liner:

  return setmetatable(self, mt)

where mt.__index has all the methods. How you assign to mt.__index can vary across modules according to style, but that's a _purely_ asethetic issue. The mechanics are identical. Using a module to accomplish it creates a useless dependency.

There are many criticisms one could make of Lua, but I don't think those two particular criticisms are legit. They're classic bikeshedding.

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The function you presented that trims to the right has quadratic runtime behavior if your string has a long sequence of spaces that is not at the end of the string. For example, "a b". A similar performance bug was behind a 30 minute downtime at stackoverflow.com, because a code snippet with 20 thousand spaces inside a comment showed up on their frontpage.

See, its not that simple :) http://lua-users.org/wiki/StringTrim

Anyway, I wasn't trying to say bad things about Lua with my examples. Its just that if you go to any large Lua project out there there is a very good chance you will find some "utils" module in there with yet another reimplementation of a lot of these common functions. Ideally we should have people reusing more stuff from Luarocks than they are right now.

If you're reading a pile of string processing code, seeing

    s.rstrip()

helps make code self-documenting, compared to

    s:gsub("%s*$", "")

I don't want to argue for a massive standard library (for instance, I don't think Python should have shipped modules for dbm, bdb, sqlite, or XML-RPC), but simple string processing seems like a good thing to standardize.

String processing is never simple. Simply identifying "what is whitespace?" is a big undertaking in Unicode.

Lua's philosophy seems to be to include the absolute minimum that is unacceptably painful to omit. This is a perfectly reasonable tradeoff for Lua's primary use case: embedding.

With respect to strings in particular, most systems that Lua is embedded in has its own string type, or inherits one from a framework. This is an unfortunate reality of the C/C++ world.

Returning to my point about language standard libraries: The lack of a traditional "standard library" is a feature for Lua, but only because Lua has a strong FFI and C API that acts as a "bring your own standard library" mechanism. It's less about needing a standard library, and more about admitting a language is only one piece of the puzzle. For a language to flourish, you need to have some story for interfacing with the rest of the world in a rich way.

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